lengthening

noun

1. The process of making or growing longer.

   “This enabled an additional 15-20 containers to be carried per train, giving a 20% productivity gain, and was partly enabled by Network Rail completing the lengthening of loops on the route northwards from Southampton via Banbury.”

2. a type of sound change when a sound (especially a vowel) lengthens

verb

1. (form-of, gerund, participle, present)present participle and gerund of lengthen