Subordinating conjunctions in Japanese grammar are essential to connect clauses or sentences expressing relationships such as cause, reason, and purpose. They indicate that the following clause is a dependent clause and explain the relationship of the clause with the main clause. Some common subordinating conjunctions in Japanese are « ので » (node), « から » (kara), « が » (ga), « けれども » (keredomo), and « ために » (tame ni). These conjunctions play a vital role in providing context and meaning to sentences, making them indispensable in Japanese communication.