lengthen vs grow

lengthen and grow both are verbs.

Word	Noun	Adjective	Verb	Adverb
lengthen	No	No	Yes	No
grow	No	No	Yes	No

As verbs, grow is a hypernym of lengthen; that is, grow is a word with a broader meaning than lengthen:

lengthen (verb)	grow (verb)
become long or longer	come to have or undergo a change of (physical features and attributes)
make longer	become larger, greater, or bigger; expand or gain
	cause to grow or develop
	increase in size by natural process
	pass into a condition gradually, take on a specific property or attribute; become
	develop and reach maturity; undergo maturation
	grow emotionally or mature
	become attached by or as if by the process of growth
	cultivate by growing, often involving improvements by means of agricultural techniques
	come into existence; take on form or shape