Lesson 20   The prefixes com and in

com + gratulate	= congratulate	in + stinct	= instinct
com + tinent	= continent	in + spection	= inspection
com + nection	= connection	in + numerable	= innumerable
com + mon	= common	in + measurable	= immeasurable
com + municate	= communicate	in + mobile	= immobile
com + mand	= command	in + mature	= immature
com + patible	= compatible	in + personate	= impersonate
com + plicated	= complicated	in + possibility	= impossibility
com + pliment	= com pliment	in + pression	= impression
com + bination	= combination	in + balance	= imbalance

A prefix may be spelled in several different ways.

1.	Look at the first three words in each column. Are the prefixes com and in spelled with an n or an m when they are added to root words to form these words? _____ Why do the words connection and innumerable have double consonants? _______________________________________
2.	Look at the remaining words in each column. How is the prefix com spelled when it is added to roots that begin with m, p, or b? _____ How is the prefix in spelled when it is added to words or roots that begin with m, p, or b? _____

Lesson Generalization The prefixes com and in follow the same spelling pattern. Both are spelled with an n before most letters of the alphabet. Both are spelled with an m before roots or words that begin with the letters m, p, or b. They are spelled this way to make more compatible combinations that are easier to pronounce. Say inmobile and immobile. Say comtinent and continent. Mnemonic device: Remember common compatible combinations. Double consonants often result from joining prefixes and roots. Remember that one consonant belongs to the prefix, and one belongs to the root.

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