The Blue Book of Grammar and Punctuation by Jane Straus, Lester Kaufman, Tom Stern Page A

guard (from feign ).
    FAIR, FARE
    Fair : an exhibition (noun); just, impartial (adjectives).
    Fare : payment for travel (noun); to have an experience (verb); to go through something (verb): How did you fare on your test?
    FARTHER, FURTHER
    The general rule: farther refers to real, physical distance: Let's walk a little farther .
    Further deals with degree or extent: Let's discuss this further .
    FAZE, PHASE
    When something or someone fazes you, you are disturbed or troubled: Her behavior doesn't faze me .
    A phase is a period or chapter: He's going through a difficult phase right now .
    FEAT, FEET
    Feat : an extraordinary act or accomplishment.
    Feet : twelve-inch increments; appendages below the ankles.
    FEWER, LESS
    Here's a seemingly innocent sentence: I now have two less reasons for going . Make it two fewer reasons . If you can count the commodity (two reasons), less will be wrong. You have less justification , but fewer reasons .
    Exception: When the amount is one , such a sentence should read, “I now have one reason fewer ” or “ one less reason, but not “ one fewer reason.” Admittedly, this is a head-scratcher, but that's English for you.
    Use less for specific measurements of money, distance, time, or weight: It costs less than a million dollars. We walked less than fifty feet. Less than thirty minutes had passed. It weighs less than five pounds . The book Modern American Usage explains why: “We take a million dollars as a sum of money, not as a number of units; fifty feet as a measure of distance, not as one foot added to forty-nine other feet; thirty minutes as a stretch of time, exactly like half an hour…and the quantitative less is therefore correct in comparisons; fewer would sound absurd.”
    FIR, FUR
    Fir : a type of tree.
    Fur : animal hair.
    FIRSTLY
    See secondly, thirdly, fourthly .
    FLAIR, FLARE
    Flair : style; talent.
    Flare : to erupt; to blaze.
    FLAMMABLE, INFLAMMABLE
    Let's see: flammable means “combustible.” Inflammable means “combustible.” Any questions?
    FLAUNT, FLOUT
    He was a rebel who flaunted the rules . That sentence is incorrect. Make it flouted the rules . To flout is to ignore, disregard, defy.
    To flaunt is to make a big display: She flaunted her diamond necklace .
    FLEA, FLEE
    Flea : a type of insect.
    Flee : to run away.
    FLOUNDER, FOUNDER
    One way to avoid confusing these two verbs is to think of flounder , the fish. Something that is floundering is thrashing around helplessly, like a fish out of water.
    Founder means “to fail.” If a business is floundering , it is in distress but may yet be saved. If a business founders , nothing can revive it.
    FLOUR, FLOWER
    Flour : an edible powder prepared by grinding grains.
    Flower : the bloom of a plant.
    FOREGO, FORGO
    Many permissive editors allow forego in place of forgo . But forego means “to go before,” “precede”: A good stretching session should forego rigorous exercise .
    To forgo is to abstain from, do without: If you forgo a good stretching session, you might pull a muscle .
    FOREWORD, FORWARD
    A foreword is an introduction, usually to a book. It's sometimes confused with forward , meaning “ahead,” “forth.”
    FORMER
    See latter .
    FORTH, FOURTH
    Forth : onward.
    Fourth : coming directly after whatever is third.
    FORTUITOUS, FORTUNATE
    Fortuitous is a chronically misunderstood word. To purists, it most emphatically does not mean “lucky” or “fortunate”; it simply means “by chance.” You are fortunate if you win the lottery fortuitously , but you can also get flattened by a truck fortuitously .
    FOUL, FOWL
    Foul : tainted; sickening.
    Fowl : edible bird or birds.
    FRACTIOUS
    See factious, fractious .
    FREE GIFT
    A curious term for gift .
    FULSOME
    Many people take fulsome to mean “abundant” or “lavish.” But be wary of writing the likes of He received a fulsome tribute or Please accept my