To lengthen is to make something longer, either physically or in time. During the spring and early summer, the days lengthen, as sundown comes later and later.

Mascara lengthens your eyelashes, and letting out your hem lengthens your jeans. As time goes by, your years of experience lengthen, and if you don't cut your hair or trim your beard, those lengthen as well. Lengthen dates from the 14th century — earlier, the verb was length, from a Germanic root that's also the basis of "long."

Definitions of lengthen

v make longer

Lengthen this skirt, please”
make shorter than originally intended; reduce or retrench in length or duration
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draw out, extend, prolong, protract
lengthen in time; cause to be or last longer
elongate, stretch
make long or longer by pulling and stretching
prolong the time allowed for payment of
temporise, temporize
draw out a discussion or process in order to gain time
spin, spin out
prolong or extend
shoetree, tree
stretch (a shoe) on a shoetree
Type of:
make bigger or more

v become long or longer

“In Spring, the days lengthen
become short or shorter
Type of:
become larger, greater, or bigger; expand or gain

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