The abuse of these words exasperates many a pedantic lover of English.
Affect, effect
Affect is usually a verb and
effect is usually a noun.
The teacher hoped to affect the students’ results.
The teacher affected a look of disbelief when the school published the results. (Here, it means to pretend or imitate.)
Psychologists say that affect is the conscious experience or emotion. (Here, it is a noun that refers to feeling.)
The teacher had a profound effect on the results.
The new teacher effected many changes in the curriculum.
Alternate, alternative
Alternate is every other one or succeeding by turns and
alternative means one of two choices or a substitute. The usage is becoming blurred, but it is worth sticking to the rules.
The nurse comes on alternate days.
The alternative is to shut it down.
Complement, compliment
Complement means to complete a whole and can be a verb or a noun.
Compliment means to praise and can also be a verb or a noun.
Her presence complements that of the family.
A complement of 20 fire fighters attended the scene.
He compliments her on the report she has written.
His compliment was sincere.
Comprise
Comprise means made up of or to include; however, it is often confused with compose or used as synonym for constitute.
NOTE: Never say “comprised of”.
The organisation comprises three divisions. (Here, the three divisions are the whole organisation.)
But:
The organisation includes the Capital Growth Division. (Here, the Capital Growth Division is part of the organisation, but not all parts are mentioned.)
Fewer, less
Fewer modifies a plural noun and refers to units that can be expressed as a specific number.
Less modifies a singular noun and refers to quantity or bulk and to comparisons that cannot be expressed numerically.
Eat less meat and you will consume less fat.
I have fewer dollars in my pocket than you have.
But:
I have less than twenty dollars in my pocket.
Stationary, stationery
Stationary is an adjective that means fixed in place.
Stationery is a noun that means writing materials, pens, envelopes.
The train was stationary for 30 minutes.
Let’s buy the stationery at the supermarket.