The Prefix Semi: A Complete Guide (Real Examples + PDF)

The prefix semi is commonly used in the English language to indicate partiality or incompleteness. It is derived from the Latin word “semi,” which means half. The addition of semi to a word can change its meaning, creating new words that are frequently used in everyday language.

The prefix semi- is used to mean “partial” or “somewhat” in words like “semicircle” or “semi-conscious.” Example: “The patient was semi-conscious after the surgery, but still unable to speak.”

In this blog post, we will explore the various meanings and uses of the prefix semi and provide examples of how it can alter the meaning of a word.

You’ll gain a deeper understanding of the prefix semi- and maybe find new ways to use it in your own English conversations. Plus, you can find a free Prefix Semi- Word List PDF download at the end of this post.

The Prefix Semi- Meaning 

The prefix semi- is used in adjectives and nouns to mean partly or half.  Semi-conscious means partly conscious. A semicircle is half a circle. 

semi_2 prefix 

Prefixes and Hyphens (-)

How can I tell if my prefix word needs a hyphen or not? That’s a great question, even for native English speakers. Hyphens are things we only need to worry about in written English, in English conversation we can’t see hyphens.

Sometimes we need to send an email so we want to use the correct spelling in our message. Here is a basic guide to using hyphens (-).

According to Grammar Monster: 

Most prefixed words can be written with or without a hyphen after the prefix.


So there is some freedom in our choice to use a hyphen or not. Our goal is to communicate our ideas clearly to our conversation partners, here are a few guidelines to help you achieve that goal in your English writing. 

  1. The prefixes- ex- and self- will always use a hyphen.
    1. Ex-wifeSelf-evaluation
  1. Break up matching vowels. This makes your message clear. This applies to prefixes that end in a vowel like CO- and DE-
    1. De-escalateCo-opt
  1. If the vowels don’t match we can usually leave out the hyphen
    1. Deactivate (No hyphen is ok.)
  2. Be careful if your prefix word looks the exactly the same or similar to another word. Adding a hyphen makes your meaning clear.
    1. For example re-cover means to cover again – The verb recover means to get well again after being ill, hurt, etc. (Using a hyphen is necessary to make the meaning of your word clear.) 
  3. Still not sure? Trust your spell checker! I use Grammarly. You can download the FREE version here: Grammarly

My choice to write the word with or without a hyphen (-) is random. Both spellings are usually fine.

The Prefix Semi- Real Examples 

Semi-annual: occurring twice a year, every six months. (I found examples of semiannual written with and without a hyphen)
The company’s board meetings are held on a semi-annual basis.
The company’s budget is reviewed on a semiannual basis.

Semi-arid: a climate or region that receives very little rainfall, but not as little as a desert.
The semi-arid region is prone to droughts and water scarcity.

The Prefix semi - semi-arrid

Most semi-arid areas usually have very little rainfall throughout the year.

Semi-automatic: a firearm that requires a trigger pull for each round fired, but uses some of the energy from firing to automate reloading.
The soldier keeps his semi-automatic rifle clean and ready for action.

Semi-detached: a type of housing where two separate dwellings share a common wall.
The new family moved into the semi-detached house next door.

Semi-final: a competition in which the winners will advance to the final round.
The team won their semi-final match and advanced to the championship game.

Semi-precious: referring to gems or stones that are not as rare or valuable as precious stones like diamonds.
She loves to wear jewelry made of semi-precious stones like amethyst and turquoise.

Semi-skilled: having some training or ability in a particular job or trade, but not fully qualified or experienced. (I found examples of semiskilled written with and without a hyphen)
The company hired semi-skilled workers to perform basic assembly line tasks.
The construction worker was semiskilled, able to perform basic tasks like framing and roofing but not qualified to do electrical or plumbing work.

Semi-sweet: referring to a taste that is only slightly sweet.
The dessert had a perfect balance of semi-sweet chocolate and tart cherries.

The Prefix semi - semi-sweet

I like semi-sweet chocolate. Dark chocolate is bitter and milk chocolate is too sweet for me.

Semi-trailer: a type of trailer that is attached to a truck tractor and is designed to carry freight without a front axle.
The truck driver hitched the semi-trailer to the tractor and set off on the highway.

Semi-tropical: referring to a climate or region that is moderately warm and humid, but not as hot as a tropical climate. (I found examples of semitropical written with and without a hyphen)
The resort is located in a semi-tropical climate that offers warm weather and cool breezes.
The region had a semitropical climate, with warm temperatures and occasional tropical storms.

Semi-weekly: occurring twice a week, every other day or twice in a week.
The newspaper publishes semi-weekly editions on Wednesdays and Saturdays.

Semiautonomous: partially self-governing, having some degree of autonomy but still under the control of a larger entity.
The city has semiautonomous districts that have some control over their own local affairs.

Semi-basement: a partially below-ground level of a building, with windows above the ground level.
The storage area in the semi-basement kept the tools and equipment cool and dry.

Semibluff: a poker play in which a player with a weak hand bets as if they have a strong hand, in order to bluff their opponents.
He made a semibluff with his low pair, hoping to scare his opponent into folding.

The Prefix semi - semibluff

If I make a big bet and turn this into a semibluff I might take the pot down now.

Semicircle: a thing, or a group of people or things, like a semicircle in shape
The teacher had everyone sit in a semicircle while we listened to the story. 

Semiconscious: a state of being partially awake or aware.
The patient was semiconscious after the surgery, but still unable to speak.

Semidependent: partially dependent on someone or something else for support or care.
The elderly woman was semidependent on her caregiver for help with daily tasks.

Semidesert: a region that is partially desert, with less extreme conditions than a full desert.
The semidesert landscape was dotted with cacti and scrub vegetation.

Cacti is an irregular plural form of the noun cactus. Learn more about singular and plural nouns at my blog post: Singular and Plural nouns – 50 examples (worksheet PDF)

Semidiameter: half the diameter of a circle or sphere.
The semidiameter of the Earth is approximately 3,959 miles. (6,378.1370 km) SOURCE

The Prefix semi - semidiameter

Semidomesticated: partially tamed or domesticated, but not fully adapted to living with humans.
The stray cat was semidomesticated, showing signs of having once lived with humans but still wary of being approached.

Semifictional: partially based on real events or people, but with fictional elements added.
The movie was semifictional, telling the story of a real-life celebrity but embellishing some of the details for dramatic effect.

Semiflexible: partially flexible, able to bend or adapt to some degree but not completely pliable.
The semiflexible plastic tubing was perfect for use in plumbing, as it could bend around obstacles but still maintain its strength.

Semifluid: partially fluid, having some fluidity but not completely liquid.
Some of the lower levels of the Earth are made of semifluid liquid rock. 

Semiformal: partially formal, having some elements of formality but not completely formal.
The dress code for the event was semiformal, allowing for some flexibility in attire but still requiring a certain level of dressiness.

The Prefix semi - semi-formal

We dress semi-formal at the office. A collared shirt without a tie is fine.

Semigloss: partially glossy, having some shine but not completely glossy.
The walls were painted with a semigloss finish, giving them a slight shine without being too reflective.

Semiofficial: partially official, having some level of authority or recognition but not completely recognized or sanctioned.
The group had a semiofficial status, with some recognition from the government but was not considered an official organization.

Semipermanent: partially permanent, lasting for an extended period but not intended to be permanent.
I work at the school on a semipermanent basis.

Semiprivate: partially private, offering some degree of privacy but not completely private.
The hospital room was semiprivate, shared with one other patient but offering a degree of privacy with a dividing curtain.

The Prefix semi - semiprivate

I had good travel insurance so I could upgrade from a semiprivate room to a private room.

Semipro / Semiprofessional: a person who is not a full-time professional, but earns money in a particular field on a part-time or occasional basis.
The soccer team had several semipro players who worked day jobs but played on the weekends.

Semiretired: partially retired, working part-time or on a reduced schedule but not fully retired.
The consultant was semiretired, working only a few days a week but still advising clients on projects.

Semisolid: partially solid, having some solidity but not completely solid.
Mayonnaise is a good example of a semisolid. It’s not completely solid but it also doesn’t flow like a liquid.

The Prefix semi - semisolid

Semitransparent: partially transparent, allowing some light to pass through but not completely transparent.
The window film was semitransparent, offering some privacy.

Semivowel: a speech sound that sounds like a vowel but functions as a consonant, for example, /w/ and /j/ in the English words wet and yet

“The words “yes” and “well” start with semivowels.”


Some of the words on this list can be referred to simply as “semi” in conversation. The full word is understood by the context of the story. 

  • “I used to live in a semi in a suburb of Toronto.”
    This means a semi-detached house. 
  • “There was a big accident on the highway, a semi rolled over and caused a huge traffic jam.”
    This means a semi-trailer rolled over. 

The plural form semis is often used to refer to the semi-final games of a sports tournament. 

  • If we win tonight we make it to the semis.

The Prefix Semi- Frequently Asked Questions 

What is the origin of the prefix semi?

The Prefix Semi- comes from Latin. It’s related to the Greek hemi-.
You may have heard the word hemisphere before, hemisphere is half of the Earth divided at the equator. We have the North and the South hemispheres

How does the use of the Prefix SEMI vary across different languages?

In English, semi- is a common prefix that is used to indicate partiality or incompleteness.

French often uses the prefix demi- to indicate partiality or incompleteness. For example, “demi-cercle” means half-circle in French, while “demi-finale” means semifinal.

In Spanish, the prefix semi- is often replaced with “medio-” or “mitad de-” to indicate partiality or incompleteness. For example, “medio círculo” means half-circle in Spanish.

In some other languages, such as German, the prefix halb- is used to indicate partiality or incompleteness. For example, “Halbkreis” means half-circle in German.

How about in your language? Share any prefixes that have the same meaning in your language in the comments

Prefix Semi- 10-page Word List PDF

Download the Word List as a printable PDF. Great for teachers to use with private or group classes. PDF contains the live links from the post.

Check out these other helpful PREFIX and SUFFIX blog posts. 

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