before a vowel emphat. prep. & adv.
prep. 1 introducing a noun: a expressing what is reached, approached, or touched (fell to the ground; went to Paris; put her face to the window; five minutes to six). b expressing what is aimed at: often introducing the indirect object of a verb (throw it to me; explained the problem to them). c as far as; up to (went on to the end; have to stay from Tuesday to Friday). d to the extent of (were all drunk to a man; was starved to death). e expressing what is followed (according to instructions; made to order). f expressing what is considered or affected (am used to that; that is nothing to me). g expressing what is caused or produced (turn to stone; tear to shreds). h expressing what is compared (nothing to what it once was; comparable to any other; equal to the occasion; won by three goals to two). i expressing what is increased (add it to mine). j expressing what is involved or composed as specified (there is nothing to it; more to him than meets the eye). k expressing the substance of a debit entry in accounting (to four chairs, sixty pounds). l archaic for; by way of (took her to wife). 2 introducing the infinitive: a as a verbal noun (to get there is the priority). b expressing purpose, consequence, or cause (we eat to live; left him to starve; am sorry to hear that). c as a substitute for to + infinitive (wanted to come but was unable to).
adv. 1 in the normal or required position or condition (come to; heave to). 2 (of a door) in a nearly closed position. to and fro 1 backwards and forwards. 2 repeatedly between the same points.
[ OE to (adv. & prep.) f. WG ]