The siida is a Sami local community that has existed from time immemorial. A siida (in different Sami languages cearru, siida, sita, kite), or a "reindeer pastoralistic district," is a Sami reindeer foraging area, a group for reindeer herding and a corporation working for the economic benefit of its members. The reindeer herding siida has formed as an adaptation of ancient siida principles to large-scale nomadic reindeer herding. It is termed a sameby ("Sami village") in Swedish law, reinbeitesdistrikt ("reindeer pasture district") in Norwegian law, and paliskunta in Finnish law. The pastoralistic organisation differs slightly between countries, except in Russia, where kolkhoz has replaced these earlier organisations.
In Sweden, membership in a siida follows "pastoralistic rights" based on statute of limitations, and is limited to individuals of Sami descent. These rights also include hunting and fishing for profit. There are 33 mountain siidas, 10 forest siidas and 8 concession siidas, divided by historical extent, summer and winter pasture usage, etc. Membership is required to practice pastoralistic rights. This is required for reindeer ownership as well, except in concession siidas, where even non-members can own "serve reindeers", served by siida members who receiving concession to pasture lands in payment. This custom originates in older conventions when reindeer were used by settled local populations in daily life. The economic activity in present-day siidas is limited to profit from pastoralistic rights. In addition to the geographical and economic nature of the siida, it also ties the members together culturally and socially.
Siidas in Sweden split Sami people into two groups. Membership is essentially limited to those whose ancestors were nomads before 1886, barring the majority of Swedish Sami from membership in a siida.
In Norway, pastoralistic activity requires membership in a unit (driftsenhet), corresponding to a reindeer herd. The rights to conduct pastoralism are based on statute of limitations and limited to individuals of Sami descent.