tendency vs leaning

tendency and leaning both are nouns.

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

As nouns, leaning is a hyponym of tendency; that is, leaning is a word with a more specific, narrower meaning than tendency:

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

As nouns, tendency and leaning are synonyms defined as:

Other synonyms of tendency include propensity.

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

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