Can you use tzatziki instead of raita?

Sure, it'll cool things down. It's thicker and much more garlicky, though, so it changes the dish more than raita would.

Usually not, since it's there to cool you down. Some versions add a pinch of chili or green chili, but cumin and mint are more common.

Tzatziki vs raita: what's the difference?

Both are cool yogurt sauces with cucumber, but Greek tzatziki is thick, garlicky and herby with dill or mint, while Indian raita is thinner, gentler and often spiced with cumin.

Tzatziki

Very light

Indulgent

Subtle

Big punch

Mellow

Zingy

Thick, tangy and garlicky, with cucumber and dill keeping it fresh.

Raita

Very light

Indulgent

Subtle

Big punch

Mellow

Zingy

Thin, cool and gentle, made to calm down a spicy curry.

The real difference

Tzatziki uses strained Greek yogurt, grated cucumber, plenty of raw garlic, olive oil and dill or mint, so it's thick enough to scoop. Raita uses regular, runnier yogurt and changes a lot: cucumber, onion, tomato, mint or fruit, often with toasted cumin. Tzatziki is a dip; raita is a cooling side.

Side by side

TzatzikiRaita

YogurtThick, strained Greek yogurtRegular, runnier yogurt

SeasoningRaw garlic, dill or mint, olive oilCumin, mint, sometimes onion or tomato

On a menuGyros, souvlaki, with pitaNext to biryani, curries, tandoori

Which to order

Order tzatziki if you want a garlicky dip for grilled meat or pita.
Order raita if your curry is hot and you want something cool on the side.

Quick questions

Can you use tzatziki instead of raita?: Sure, it'll cool things down. It's thicker and much more garlicky, though, so it changes the dish more than raita would.
Is raita spicy?: Usually not, since it's there to cool you down. Some versions add a pinch of chili or green chili, but cumin and mint are more common.