leaning vs tendency

leaning and tendency both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaning	Yes	Yes	No	No
tendency	Yes	No	No	No

As nouns, tendency is a hypernym of leaning; that is, tendency is a word with a broader meaning than leaning:

leaning: a natural inclination
tendency: an attitude of mind especially one that favors one alternative over others

Other hypernyms of leaning include disposition, inclination.

As nouns, leaning and tendency are synonyms defined as:

Other synonyms of leaning include propensity.

leaning (noun)	tendency (noun)
the act of deviating from a vertical position	a characteristic likelihood of or natural disposition toward a certain condition or character or effect
the property possessed by a line or surface that departs from the vertical	an attitude of mind especially one that favors one alternative over others
a natural inclination	an inclination to do something
an inclination to do something	a general direction in which something tends to move

leaning (adjective)	tendency (adjective)
departing or being caused to depart from the true vertical or horizontal