happen vs develop

happen and develop both are verbs.

Word	Noun	Adjective	Verb	Adverb
happen	No	No	Yes	No
develop	No	No	Yes	No

As verbs, develop is a hyponym of happen; that is, develop is a word with a more specific, narrower meaning than happen:

happen (verb)	develop (verb)
come to pass	come to have or undergo a change of (physical features and attributes)
come into being; become reality	grow, progress, unfold, or evolve through a process of evolution, natural growth, differentiation, or a conducive environment
happen, occur, or be the case in the course of events or by chance	cause to grow and differentiate in ways conforming to its natural development
come upon, as if by accident; meet with	happen
chance to be or do something, without intention or causation	change the use of and make available or usable
	be gradually disclosed or unfolded; become manifest
	gain through experience
	become technologically advanced
	grow emotionally or mature
	expand in the form of a series
	elaborate by the unfolding of a musical idea and by the working out of the rhythmic and harmonic changes in the theme
	create by training and teaching
	elaborate, as of theories and hypotheses
	move into a strategically more advantageous position
	move one's pieces into strategically more advantageous positions
	superimpose a three-dimensional surface on a plane without stretching, in geometry
	work out
	make something new, such as a product or a mental or artistic creation
	generate gradually
	make visible by means of chemical solutions
	come into existence; take on form or shape