worry vs obsess

worry is a noun but obsess is not a noun.

Word	Noun	Adjective	Verb	Adverb
worry	Yes	No	Yes	No
obsess	No	No	Yes	No

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

Other hyponyms of worry include fret, fear, fret, fuss, niggle.

worry (noun)	obsess (noun)
something or someone that causes anxiety; a source of unhappiness
a strong feeling of anxiety

worry (verb)	obsess (verb)
lacerate by biting	haunt like a ghost; pursue
touch or rub constantly	be preoccupied with something
be worried, concerned, anxious, troubled, or uneasy
disturb the peace of mind of; afflict with mental agitation or distress
be concerned with
be on the mind of