pennywhistle vs vertical flute

pennywhistle and vertical flute both are nouns.

Word	Noun	Adjective	Verb	Adverb
pennywhistle	Yes	No	No	No
vertical flute	Yes	No	No	No

As nouns, vertical flute is a hypernym of pennywhistle; that is, vertical flute is a word with a broader meaning than pennywhistle:

pennywhistle: an inexpensive fipple flute
vertical flute: a tubular wind instrument with 8 finger holes and a fipple mouthpiece

Other hypernyms of pennywhistle include fipple flute, fipple pipe, recorder.

pennywhistle (noun)	vertical flute (noun)
an inexpensive fipple flute	a tubular wind instrument with 8 finger holes and a fipple mouthpiece