Word parts change

length + -en

Pronunciation change

Verb change

Plain form
lengthen

Third-person singular
lengthens

Past tense
lengthened

Past participle
lengthened

Present participle
lengthening

  1. (transitive) If you lengthen something, you make it longer in length or duration.
  2. (intransitive) If something lengthens, it becomes longer in length or duration.