Rest in peace (acronym R.I.P.) in the second person singular, or “Requiescite in pace” in the second person plural. In the common phrase "Requiescat in pace" the "-at" ending is appropriate because the verb is a third-person singular present active subjunctive used in a hortative sense: "May he/she rest in peace." The phrase was first found on tombstones some time before the fifth century. It became ubiquitous on the tombs of Christians in the 18th century, and for High Church Anglicans, Methodists, as well as Roman Catholics in particular, it was a prayerful request that their soul should find peace in the afterlife.
Phrase qualifies as a phrase, and the head-word gives its syntactic name, "subordinator", to the grammatical category of the entire phrase. But this phrase, "before that happened", is more commonly classified in other grammars, including traditional English grammars, as a subordinate clause (or dependent clause); and it is then labelled "not" as a phrase, but as a clause. Most theories of syntax view most phrases as having a head, but some non-headed phrases are acknowledged. A phrase lacking a head is known as exocentric, and phrases with heads are endocentric. Some modern theories of syntax introduce certain functional categories in which