The word zero has a small but distinctive set of synonyms, which are listed in this post.
Zero is the word for the symbol 0, representing the absence of magnitude or quantity and the value between positive and negative numbers. The word also represents the lowest point or the starting point for measurement or, as in the phrase “ground zero,” a point of impact or origin. In addition, it refers to absence or impartiality, or to the lowest possible score on a test, and as slang it describes a worthless person or one with little or no discernible charm or personality.
The word ultimately derives, like many arithmetical and scientific terms, from Arabic, in this case sifr, which means “zero” or “empty” and is also the source of the synonym cipher. Meanwhile, cipher itself, while also occasionally expressing the numerical symbol, describes a nonentity, with the connotation that a person so identified has no influence or no distinguishing characteristics, as in a reference to someone mysteriously vague. This sense of mystery extends to the sense for cipher of a method of encoding information, or a coded message itself. A cipher may also be a combination of letters used symbolically, similar to a monogram.
Aught and naught, discussed in more detail in this post, are also synonyms of zero (as is nought, a variant of the latter word), but briefly, aught is employed usually when referring to the first decade of a century (in which the tens place of any given year is represented by a zero) or to a zero used in decimal measurement. Naught, however, is used in the sense of “nothing.”
Nothing itself, as might be guessed, literally means “no thing” and stems from Old English. In addition to pertaining to a lack of quantity, nothing alludes to nonexistence and is used, like zero, to suggest that someone is worthless. However, it also, in plural form, refers to playful remarks, especially, as part of “sweet nothings,” in a romantic context. It is also employed, though rarely, as an adjective or adverb.
Nil, a contraction of the Latin word nihil (the root of nihilism, the word for a philosophy of renunciation of traditional ideas or morals), is ultimately from nihilum, literally “not (even) a trifle,” and generally alludes to a comparison, such as a sports score or to the distinction, or lack thereof, between two like objects, or to (a lack of) probability; one’s chances of achieving an impossible result, for example, are said to be nil.
Zilch and zip, both of obscure origin, are slang synonyms for zero. The letter o and the word oh are also, because of the resemblance of the letter to the symbol for zero, used informally in speech and rarely in writing to refer to the symbol, as is “goose egg,” from the similarity in shape between that object and the symbol. (On a related note, the use of love to indicate a zero score in tennis is said to originate in the phrase l’oeuf, French for “the egg,” though this etymology is disputed.)