Both words refer to the act of coming to or reaching a place. Arrival suggests reaching a place by someone or something that has been moving through space towards this place: airport arrivals; the arrival of refugees. Arrival can also be used to mark time: before the arrival of electricity. Advent is also frequently used to speak of the arrival or beginning of something or someone of significance, including day and night and seasons, but particularly historical developments or advances: the advent of computers, agriculture, or summer. Used in this way, advent is not the result of a journey in any recognizable sense, but more an appearance, beginning, or becoming present.

Both these adjectives are more formal synonyms for “nonstop.” Constant, the more frequent word, describes something that continues without stopping or pausing: under constant pressure. In this sense, constant often (though not always) has a negative connotation—and unremitting more so, as it suggests never even letting up or abating, let alone ceasing. The nouns that appear most commonly with unremitting are pain, effort, stress, hostility, bleakness, and pressure, and the verbs, endure and withstand. However, unremitting is sometimes used to describe an admirable and faithful effort, and can even, through contrast with its usual associations, evoke a powerful good: unremitting kindness.

Stuff has over a dozen dictionary definitions for the noun form alone. The sense of “personal belongings” (all his stuff) is the focus here. If the stuff in question is composed of things used for a particular purpose (drug paraphernalia; sewing paraphernalia), or of memorabilia and other themed items (Grateful Dead paraphernalia), paraphernalia is a strong synonym. But there is another, much less common sense of paraphernalia that means “personal belongings.” Historically, paraphernalia was women’s stuff: as a legal term it meant things a woman owned that were not included in her dowry and therefore not her husband’s property—usually clothing and personal items. So paraphernalia could be an interesting synonym for stuff (a purse jammed with her paraphernalia) if its predominant association with illegal drug use doesn’t interfere with the intended meaning.