Many words are made up of a root word and an affix. An affix is a word part that is attached to the beginning or the end of a root word; this affix then changes the meaning of the root word.

A prefix is a word part that is added to the beginning of a word to create a new meaning. For example, if the prefix “un” is added to the root word “happy”, we get a new word that has the opposite meaning to happy: “unhappy”.

A suffix is a word part that is added to the end of a word to create a new meaning. For example, if we take the root word “care”, we can change its meaning by adding the suffix “ful”, to give us the word “careful” (meaning “cautious” or “paying attention”). Alternatively, we could add the suffix “less” to “care”, to give us a word with a very different meaning: “careless” (meaning “not concerned” or “lacking in attention”).

Many words that we use in science use prefixes and suffixes that are derived from Greek or Latin. While this may seem complicated, once you become familiar with some of these prefixes and suffixes you will often be able to work out the meaning of scientific words, even if they are new to you.

Consider this example:

The word part “cyte” is derived from the Greek word for “cell”.

The word part “erythro” is derived from the Greek word for “red”.

The word “erythrocyte” means “red blood cell”.

The word “leucocyte” means “white blood cell” (the word part “leuco” being derived from the Greek word for “white”).

Note that some affixes can act as suffixes or as prefixes, depending on the word they are being used in.

For example, in the word “cytology”, meaning “the study of cells”, the word part “cyte” appears at the beginning of the word, rather than at the end as it does in “erythrocyte”. The word part “ology” comes from the Greek word that means “the study of”.

Exercise

Look at the list of affixes below. Then, based on this list, answer the following questions.

• Endo – within
• Exo – outside
• Iso – equal
• Macro – large
• Micro – small
• Ology – the study of
• Therm – temperature

Questions

• What is the term for an animal’s skeleton that is inside its body?
• What is the term for an animal’s skeleton that is outside its body?
• What is the term for a process in which a system changes, for example, its pressure or volume, but the temperature remains the same?
• If the word part “osteo” comes from the Greek word for “bone”, what is the scientific name for a “bone cell”?
• What is the word part missing from the list of affixes that is needed to make a word that means the study of tiny living things?

Answers are below.

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Answers

• What is the term for an animal’s skeleton that is inside its body? “endoskeleton”
• What is the term for an animal’s skeleton that is outside its body? “exoskeleton”
• What is the term for a process in which a system changes, for example, its pressure or volume, but the temperature remains the same? “isothermal”
• If the word part “osteo” comes from the Greek word for “bone”, what is the scientific name for a “bone cell”? “osteocyte”
• What is the word part missing from the list of affixes that is needed to make a word that means the study of tiny living things? “bio”