sending vs transmitting

sending and transmitting both are nouns.

Word	Noun	Adjective	Verb	Adverb
sending	Yes	No	No	No
transmitting	Yes	No	No	No

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

sending: the act of causing something to go (especially messages)
transmitting: the act of sending a message; causing a message to be transmitted

Other hyponyms of sending include transmission, transmittal.

sending (noun)	transmitting (noun)
the act of causing something to go (especially messages)	the act of sending a message; causing a message to be transmitted