"Support" is not one thing. Depending on your situation, the type and legal basis of the claim differ.
1. Interim spousal support
Awarded during divorce proceedings to the needy spouse. Ends when the divorce decree becomes final.
2. Post-divorce spousal support (yardım nafakası)
For the less-at-fault spouse who would fall into poverty due to the divorce. Usually for life or until remarriage.
3. Child support (iştirak nafakası)
For children with the custodial parent. Continues until majority or end of higher education.
4. Family support (yardım nafakası)
For ascendants and descendants in need, owed by first-degree relatives with means.
Calculation
Obligor's income, claimant's need, social context. No fixed formula — judicial discretion based on evidence.
Modification
If circumstances materially change (income, health, number of children), either party can sue to raise or lower the amount.