na-adjective
Computing term describing operations that occur in a coordinated, time-dependent manner, often contrasted with 非同期 (asynchronous).
このシステムは同期的な通信プロトコルを使っている。
This system uses a synchronous communication protocol.
同期 is the noun form meaning synchronization; 同期的 is the adjectival form.
Derived from 同期 (synchronization) + 的 (adjectival suffix).