first moment vs expectation

first moment and expectation both are nouns.

Word	Noun	Adjective	Verb	Adverb
first moment	Yes	No	No	No
expectation	Yes	No	No	No

As nouns, first moment and expectation are synonyms defined as:

first moment and expectation: the sum of the values of a random variable divided by the number of values

Other synonyms of first moment include arithmetic mean, expected value.

first moment (noun)	expectation (noun)
the sum of the values of a random variable divided by the number of values	belief about (or mental picture of) the future
	the sum of the values of a random variable divided by the number of values
	the feeling that something is about to happen
	anticipating with confidence of fulfillment