A song in three has three beats in the bar. You can count one-two-three, one-two-three. The first beat is the strong one.
The song page prints the count next to the key, as 3/4 when the song is in three. That number is the chart, not a suggestion to ignore.
A waltz feel and a hymn in three are not the same mood. They share the count. They do not share the tempo.
Amazing Grace is in three, on G, C and D. Count the three beats even when the chord holds. A held chord is not a reason to stop counting.
Silent Night is in three, on C, G7 and F. The tempo is slow. The count is still three. Do not turn it into four to make it easier.
Greensleeves is in three. The chart uses more than three chord names. Count first. Learn the extra names second.
Santa Lucia is in three, with C, G7, F and Dm. Brahms Lullaby is in three on C, G7 and F. Minuet in G is in three on G, C and D.
Each cell is time. In three, a cell that lasts one bar lasts three beats. A cell that lasts two bars lasts six beats. The table groups them so you are not counting tiny slices.
Be Thou My Vision is a hymn in three. Für Elise is a classical page in three. We Wish You a Merry Christmas is a carol in three with a longer list of names.
Clap one-two-three before you play. If the clap leans into four, you have left the song. Go back to the clap.
The Metronome with chords can tick every beat. Land the chord change on beat one. If you land on beat two, you will feel late for the rest of the bar.
Ode to Joy is in four. Do not play it in three to match this guide. Open a page whose header says 3/4.
G major and C major both contain songs in three and songs in four. The key does not decide the count. The song page does.
Three-chord Song is a three-chord loop, not a promise of three beats. Read the pattern page for its own pulse. Read the song page for the song.
When the count holds for a whole page, you can sing. Until then, the count is the piece. The tune can wait one more pass.