I mean, it seems like pretty elementary words that can occur in different type of situations. Why wouldn't they exist ?
English once did not have words for "yes" and "no" as they are precisely used today.
Yes, for example, comes from ge (whence "yea") + sie, a subjunctive form of to be (beon). It literally meant "It is so."
No in fact meant "not ever". From Etymonline:
"negative reply," early 13c., from Old English na (adv.) "no, never, not at all," from ne "not, no" + a "ever." First element from Proto-Germanic *ne (source also of Old Norse, Old Frisian, Old High German ne, Gothic ni "not"), from PIE root *ne "no, not" (see un- (1)). Second element from PIE *aiw- "vital force, life, long life, eternity" (see aye (adv.)).
It was only over time that the two words became the simple answer words meaning "yes" and "no."
In that sense, Latin certainly does have words for "yes" and "no," they're just not so simple. In Late Latin, for example, two ways emerged in Gaul to mean yes: simple hoc and hoc ille. The former became oc in Occitan and the latter became oui in French, thus dividing Medieval French languages. (Obviously there were more and greater distinctions, but it's the one that the people picked up on, for some reason.)
In Classical Latin, we have a plethora of words that are used to affirm or negate questions depending on exact usage. Note though that the simplest way is by repeating the verb: "Amasne?" "Amo!" "Visne?" "Nolo." You could even elide the verb from a negative response, which leave only the non. I like Sebastian's example from Cicero:
Cicero, Pro Rosc. Am. 54: Exheredare filium voluit. Quam ob causam? 'Nescio.' Exheredavitne? 'Non.'
The non is short for non exheredavit, but it here already is functionally similar to the English "no." This dual meaning carries over into French, Spanish, and Italian, all of which use no/non to negate a verb and as a negative answer to a general question.
For affirmative words, you typically see ita, sic (whence Spanish sí), vero, or some combination. In more unusual cases, you'll also see immo.
Sic typically means "so" and wasn't the most common way, but because of its influence on the Romance languages, I see it very often online today. See the Lewis and Short entry:
- In answers, yes = the French, Italian, and Spanish si (ante - class. and rare): Ph. Phaniam relictam ais? Ge. Sic, Ter. Phorm. 2, 2, 2: De. Illa maneat? Ch. Sic, id. ib. 5, 3, 30: Ch. Sicine est sententia? Me. Sic, id. Heaut. 1, 1, 114.
Ita was a more common way. Like sic, it also means "thus" or "so." It quite often is strengthened by additional adverbs, like vero "truly" (which could be "yes" on its own), profecto "indeed", prorsus "straightaway, truly", or plane "plainly."
For negations, while I noted the most common way above, the verb doesn't always have to appear. You can have a simple non, cf. Cicero's Pro Roscio:
"exhereditavitne (pater filium)? Non." Cic. Rosc. Am. 19.54
Lewis and Short list further examples:
Cic. Verr. 1, 7, 20; id. Ac. 2, 30, 97; id. N. D. 1, 25, 70.—（τ) In questions, non expresses surprise, and doubt of the possibility of denial (v. Madv. Gram. § “451): non sum ego servus Amphitruonis Sosia?” Plaut. Am. 1, 1, 247: “non tu scis, etc.?” id. ib. 2, 2, 71: “haec non turpe est dubitare philosophos, quae ne rustici quidem dubitant,” Cic. Off. 3, 19, 77; id. Leg. 3, 20, 47: “Quid? aviam tuam pater tuus non manifesto necavit,” id. Clu. 14, 40.
Interestingly, you can also combine it with ita: ita non est: "It is not so."
For a very strong negation, you could use minime! "the least!" or "not at all," or numquam "never." However, that's not so different from English:
"Do you want to be with me?" "Ha! Never!"
In mea sententia, this sounds like a case where a speaker of one language cannot comprehend the thought process behind the speaker of another language. Everyone has experienced it if they have come across an idiom that, when translated literally, simply doesn't make sense. However, to the people that used that idiom, it made perfect sense, as it was accompanied by the cultural context needed to understand it. As C. M. Weimer points out, every language has its own version of the affirmative and negative. In English, we use "yes" and "no" and take them to mean the same thing respectively. In Latin, however, the Romans would have used sic, minime, et cetera as "yes" and "no". But when we, English speakers, translate these words, we get definitions such as "thus" or "in the least." It's at this point where idioms become important. Although the word itself doesn't literally mean "yes" or "no," it was used in the same context as those words and are thus synonyms.
Context has always been incredibly important to our understanding of language. It is, in fact, the reason we can translate anything. Words of one language used in similar situations as words of another language can yield a translation between the two, even if the words don't mean exactly the same thing. Babies also learn language through context, by associating objects and ideas with the words used to describe them. And this, in turn, is why it is often difficult to understand foreign idioms and new languages, because our more developed brains must learn to associate new words to a new context. This becomes more difficult as we get older and the neurons associated with language become less malleable.
So I apologize for going on a psychological tangent there, but this idea has always been quite interesting to me. Although I do not reach a different conclusion to C. M. Weimer, I do provide some science background to this topic which may be useful to know. To summarize both of our answers: There are words that, in context, meant "yes" and "no" in Latin, even if they don't translate literally to those definitions.
Some people think that Romanian "da" (yes) could come from Latin "ita", even though the majority believe it is a loanword from Slavic. Here is an interesting paper on the etymology of Romanian "da" http://www.diacronia.ro/ro/indexing/details/A5256/pdf.
Late Latin words for 'yes' Northern France: Hoc ille Southern France: Hoc Spain, Portugal, Italy: Sic
In Spanish, eso is sometimes used to mean 'yes', 'that's right' etc. so maybe "ipsum" was used in Latin like that too? (in the Iberian peninsula anyway)
I like the answer that was already selected, but wanted to add a different perspective.
Although we think of "yes" and "no" as simple basic words, this distribution of words to respond to yes-or-no questions is not at all universal among languages. I know a lot that don't use the same set of words to respond to questions.
In French (Si) and German (doch) (and I think in Swedish), there are three words you have to choose from. In these systems, there is a separate word to answer a negatively phrased question in the positive. In French, if someone says: "Aren't you going?" ("Tu ne viens pas?") You would answer with "Si, je viens," rather than with "oui," if you are indeed going. I'm less sure about the parameters around the German words "ja," "doch," and "jawohl"; however, I think there are similar issues as in French.
Irish, like Latin has no words for "yes" and "no." Instead, you simply use a short form of the verb in the positive or negative to respond. In Brazilian Portuguese, there are words for "yes" and "no," but preferably you just respond with the appropriate form of the verb and maybe add an extra "no/not" at the end of a negative expression.
Outside of European languages, it is quite common for languages to use expressions that actually mean "correct" or "incorrect." In other words, you would answer the question "Aren't you going" with what seems like the word for "no," if you actually are going, in order to show that the form of the question is incorrect. Japanese works this way, and at least two west African languages I know about. Chinese has this tendency, but tends to use a wider array of responses depending on the form of the question and your intention/mood (shi 是, shi de 是的, bu shi 不是, bu 不，dui 对, bu dui 不对, duile 对了). Chinese also frequently uses a form of yes-or-no question that is phrased as an alternative of positive and negative, in that case you just respond with the appropriate form of the verb, rather than using any of the expressions above.
All this is to say that the English words "yes" or "no" actually have a lot of semantics and syntax hidden in them that does not actually translate to many languages. Indo-European seems to have been one of those languages that lacked such a word and such a system, and so Latin had nothing to inherit. Most of the daughter languages developed some sort of words and some sort of system, with differing details, but at least one, Irish, still hasn't and may never.