The seventh note in the sol-fa singing system: do, re, mi, fa, so(l), la, ti — then do again. It is the note just below the top do, and it has a strong pulling feeling, as if it wants to rise and finish on do. Most students meet it through "Do-Re-Mi" in The Sound of Music, where the line is "Tea, a drink with jam and bread" — a pun, because "ti" is said exactly like "tea". You may also see it written "te" in British books, and older books use "si" instead. That older "si" is the real story: the seventh note was called si for centuries, and someone deliberately changed it to ti so that all seven notes would begin with different letters — with si, both so and si started with s, which is confusing when you write them as single letters (d r m f s l t). Note that this is a name for a position in the scale, not a fixed pitch: in movable-do teaching, which is what most schools use, ti is whatever note sits seventh in the key you are singing in.