lengthen

verb

1 he followed her, lengthening his stride to keep up:

elongate, make longer, stretch out, extend;

expand, widen, broaden, enlarge.

▷antonyms shorten.

2 they flower in the spring when the days are lengthening:

grow longer, get longer, draw out, stretch.

▷antonyms contract, decrease.

3 you'll need to lengthen the cooking time:

prolong, make longer, increase, extend, expand, protract, stretch out, draw out, drag out, spin out.

▷antonyms curtail, truncate.

lengthen Oxford Dictionary of English