Sam (pronounced "sum", first beat) is the magnetic centre of every taal cycle. When you hear an audience erupt at a particular moment in a Hindustani concert, it is almost always because the soloist and tabla player have arrived together at sam — after a long improvised passage of taans, tihais, or layakari that calculated precisely to land on the first beat of the next cycle.
In notation, sam is marked with a special symbol (typically "X" or "+"). In hand-counting, it is marked with a clap of the hand. In a 16-beat Teen Taal, sam is beat 1; in a 12-beat Ek Taal, sam is beat 1; in 10-beat Jhap Taal, sam is beat 1 — always the cycle's beginning. After sam comes one or more taals (other claps) and a khali (a silent beat, marked with a wave of the hand). The structure of every taal is built around where sam falls and how the cycle returns to it.
Mathematically, calculating to sam is what makes tihai construction possible — the threefold repetition must land precisely on sam to resolve. Layakari (rhythmic play) sets up tension; sam releases it.
Sam is also a metaphor — the place all music returns to, the resolution at the end of struggle. Performers often speak of "landing on sam" as both a technical achievement and a spiritual one. Missing sam is one of the few visible errors in a concert; landing on sam with confidence and precision after a long detour is one of the most satisfying.