"Send in" is a common phrase used in many contexts that usually refers to the act of submitting or delivering a certain document, application, or request. However, in order to diversify your language and enhance your communication skills, it is essential to learn some synonyms for this phrase. Some possible alternatives to "send in" include: submit, send off, forward, dispatch, mail, transmit, deliver, hand over, turn over, or transfer. These synonyms can be used interchangeably depending on the context and tone, to add flavor and variety to your writing or speech. By mastering these synonyms, you can become a more proficient and versatile communicator.