for

Etymology

From Middle English for, from Old English for (“for, because of”), from Proto-Germanic *furi (“for”), from Proto-Indo-European *preh₂-. Cognate with West Frisian foar (“for”), Dutch voor (“for”), German für (“for”), Danish for (“for”), Swedish för (“for”), Norwegian for (“for”), Icelandic fyrir (“for”), Latin per (“by, through, for, by means of”) and Romance language successors (e.g. Spanish para (“for”)), Ancient Greek περί (perí, “for, about, toward”), Lithuanian per (“by, through, during”), Sanskrit परि (pári, “over, around”).

conj

1. Because, as, since.
   I had to stay with my wicked stepmother, for I had nowhere else to go.
   […]Dismount thy tuck, be yare in thy preparation, for thy assailant is quick, skillful and deadly. c. 1601, William Shakespeare, Twelfth Night, act 3, scene 4
   […]nor is there found, in sea or on land, a sweeter or pleasanter of gifts than she; for she is prime in comeliness and seemlihead of face and symmetrical shape of perfect grace; her check is ruddy dight, her brow flower white, her teeth gem-bright, her eyes blackest black and whitest white, her hips of heavy weight, her waist slight and her favour exquisite. 1885, Richard Francis Burton, The Book of the Thousand Nights and a Night
   "By means of the Golden Cap I shall command the Winged Monkeys to carry you to the gates of the Emerald City," said Glinda, "for it would be a shame to deprive the people of so wonderful a ruler." 1900, L[yman] Frank Baum, chapter 23, in The Wonderful Wizard of Oz

prep

1. Towards; in the direction of.
   The astronauts headed for the moon.
   Run for the hills!
   He was headed for the door when he remembered.
2. Directed at; intended to belong to.
   I have something for you.
3. In order to help, benefit, gratify, honor etc. (someone or something).
   Everything I do, I do for you.
   We're having a birthday party for Janet.
   The mayor gave a speech for the charity gala.
   You, telling me the things you're gonna do for me. 1976, Michael McDonald (lyrics and music), “Takin' It to the Streets”, performed by The Doobie Brothers
4. To be used or treated in a stated way, or with a stated purpose.
   This is a new bell for my bicycle.
   The cake is for Tom and Helen's anniversary.
   These apples here are for eating. The rest are for throwing away.
5. Supporting, in favour of.
   All those for the motion, raise your hands.
   Who's for ice-cream?
   I'm for going by train
   Ten voted for, and three against. (with implied object)
6. Because of.
   He wouldn't apologize; and just for that, she refused to help him.
   He looks better for having lost weight. (UK usage)
   She was the worse for drink.
   I like her for lots of reasons.
   "A summerly day for you," said my host; "You ought to be here in winter. It is impossible then to get out of the doors for the snow and wind. Ugh! dreadful weather!" 1867, Frederick Metcalfe, The Oxonian in Iceland, page 202
   I could not see his hands, for the thick gloves he wore, and his face was partially concealed by a red woollen comforter; but his entire appearance and manners tallied with what I had seen of Yorkshire farmerhood. 1864, George Etell Sargent, The Story of a City Arab, page 313
7. Intended to cure, remove or counteract; in order to cure, remove or counteract.
   This medicine is for your cough.
   I need to spray my house for termites.
8. Over (a period of time).
   I've lived here for three years.
   They fought for days over a silly pencil.
   To guide the sun's bright chariot for a day. 1717, Joseph Addison, Metamorphoses
9. Throughout or across (a distance in space).
   I can see for miles.
10. Used to introduce a subject within a to-infinitive clause.
    It is unreasonable for our boss to withhold our wages.
    All I want is for you to be happy.
11. On behalf of.
    I will stand in for him.
    I speak for the Prime Minister.
12. In the role or capacity of; instead of; in place of.
    I used a hay bale for a bed.
    He's got a turnip for a brain.
13. In exchange for; in correspondence or equivalence with.
    I got five hundred pounds for that old car!
    He matched me blow for blow.
14. In order to obtain or acquire.
    I am aiming for completion by the end of business Thursday.
    He's going for his doctorate.
    Do you want to go for coffee?
    People all over Greece looked to Delphi for answers.
    Can you go to the store for some eggs?
    I'm saving up for a car.
    Don't wait for an answer.
    What did he ask you for?
15. By the standards of, usually with the implication that those standards are lower than one might otherwise expect; considering.
    Fair for its day.
    She's spry for an old lady.
    He's very mature, for a two-year old.
16. To be, or as being.
    Don't take me for a fool.
    17th century Abraham Cowley, Of Wit We take a falling meteor for a star.
    if a man can be persuaded and fully assured of anything for a truth without having examined, what is there that he may not embrace for truth ?
    Most of our ingenious young men take up some cry'd-up English poet for their model. c. 1690, John Dryden, Translations (Preface)
    But let her go for an ungrateful woman. 1712, Ambrose Philips, The Distrest Mother
    They knew him for a stranger. 1976, Louis L’Amour, chapter 2, in The Rider of Lost Creek, Bantam Dell
17. (usually in the phrase 'for all') Despite, in spite of.
    For all his expensive education, he didn't seem very bright.
    "You must keep your head. There is still hope." "Hope!" "Yes; plentiful hope -- for all this destruction!" 1898, H.G. Wells, The War of the Worlds, London: William Heinemann, page 113
    1892 August 6, "The Unbidden Guest", in Charles Dickens, Jr. (editor), All the Year Round, page 133, Mr. Joseph Blenkinshaw was perhaps not worth quite so much as was reported; but for all that he was a very wealthy man […]
    For all his faults, there had been something lofty and great about him - as a judge, as a patron of education, as a builder, as an international figure. 1968, J. J. Scarisbrick, Henry VIII, page 240
18. Indicating something desired or anticipated.
    O for the wings of a dove.
    Ah! for wings to soar …
    And now for a slap-up meal!
    Oh! but to breathe the air / By their side under summer skies! To watch the blush on their cheeks, / The light in their liquid eyes. / Oh! but for one short hour, / To whisper a word of love; […] March 27 1858, “The Lay of the Brief”, in Punch, Or, The London Charivari, page 129
19. (in expressions such as 'for a start') Introducing the first item(s) in a potential sequence.
    Go scuba diving? For one thing, I can't even swim.
20. (with names, chiefly US) In honor of; after.
    He is named for his grandfather.
21. Due for or facing (a certain outcome or fate).
    He totally screwed up that project. Now he's surely for the sack.
22. (chiefly US) Out of; used to indicate a fraction, a ratio
    In term of base hits, Jones was three for four on the day
23. (cricket) Used as part of a score to indicate the number of wickets that have fallen.
    At close of play, England were 305 for 3.
24. (obsolete) Indicating that in prevention of which, or through fear of which, anything is done.
25. Used in various more-or-less idiomatic ways to construe individual verbs, indicating various semantic relationships such as target, purpose, result, etc.; see also the entries for individual phrasal verbs, e.g. ask for, look for, stand for, etc.
    to account for one's whereabouts    to care for a relative    to settle for second best    to allow for mistakes
26. (nonstandard) So (that), in order to
    He took the swing shift for he could get more overtime.