Comprise - is a verb meaning to consist of or be composed of.

Compose - to make up the constituent parts of.

The USA comprises 50 states.

The USA is composed of 50 states.

(Confusable words, n.d., para.8)

Accept - is a verb and has many meanings among which are to receive something.

Except - is a preposition meaning 'with the exclusion of'.

I would like you to accept this gift.

All his friends came to the party except Jim who was in hospital.

(Confusable words, n.d., para.9)

Imply - To express or indicate indirectly.

Infer - To conclude from evidence or premises.

Somebody will imply something and the recipient of the implication will infer from it.

She tried to imply that I could not understand the question.

From what he said, I was able to infer that he did not understand the situation.

(Confusable words, n.d., para.11)

Historic -means having importance in or influence on history.

Historical - means 'of or relating to the character of history.'

It was a wet day when Cook set off on his historic voyage.

The archaeological find was of major historical significance.

(Confusable words, n.d., para.14)

Economic - of or relating to the economy.

Economical - thrifty and prudent in management.

The country was experiencing a period of sustained economic growth.

The minister was accused of being somewhat economical with the truth.

(Confusable words, n.d., para.26)

University of Bristol. Faculty of Arts. (n.d.). Confusable words. Retrieved October 2, 2012, from http://www.bristol.ac.uk/arts/exercises/grammar/grammar_tutorial/page_20.htm