perioda

1. (of repeating decimals) period
   Decimalni broj 0,272727… ima periodu 27. — The decimal 0.272727… has the period 27.
2. dated (of time) period of time
   U toj periodi mnogo je putovao. — During that period he travelled a lot.
3. (in chemistry) period in the periodic table
   Natrijum i hlor se nalaze u trećoj periodi. — Sodium and chlorine are in the third period.

For a span of time, and in physics (period oscilovanja), the usual word is period (masculine); perioda (feminine) survives in Serbia mainly in school maths and chemistry, for the repeating group of digits in a decimal and for a row of the periodic table.