Crotchet
/ˈkrɑːtʃɪt/
Definition 1 of 2
Pro Tip 1/3Music Length
Crotchet indicates the time a note should be held in music, not the pitch or loudness. 
Make sure to hold that crotchet for a full beat.
Pro Tip 2/3Beat Unit
In 4/4 time, a crotchet matches the beat the metronome clicks—each click is one crotchet. 
You'll hear four crotchets per measure in most pop songs.
Pro Tip 3/3Music Sheets
On sheet music, a crotchet is noted with a filled-in oval note head and a straight stem. 
Look for the crotchets; they should be easy to spot.