The answer? Of course you can, but because of the many ways members of the BDSM community play, it becomes necessary in many circumstances to use other words or even actions to stop play when someone is uncomfortable with what is happening in a scene.
Recently, my slave did a post on our Facebook page, asking what people used as safe words. A person who claimed to have left the page (and I have no reason to doubt it) called most of the answers "toxic" and made clear that they did not understand the many nuances of BDSM. Before this same person claims that I'm gaslighting here: they did not ask any questions or run through any hypotheticals that might make them draw less nefarious conclusions about the safe words used.
I did find it alarming that one person said that they didn't use safe words at all and did not want to stop play for any reason. There can ALWAYS be a reason--I have had a medical reason to stop play, and believe me, that can happen to anybody.
But yes, "No" can be all you need, depending on the way you play. But as my slave mentioned, her safe phrase is "Master, I'm weak." The person thinking that it's a toxic thing to have her say probably thinks it's some sort of mind fuck, and I understand that perspective. However, my partner is into humiliation; she finds this safe phrase absolutely hot. She knows she's not a weak person. In fact, nearly every partner I have chosen to be with was a strong, independent woman who was very selective about who dominated them, and often dominated other men and/or women. The ones who were purely submissive sexually were also strong women. Hey, I have a type. I love a challenge.
Another reason "no" doesn't work for my slave is that she is into consensual non-consent. "No" is part of that type of play. "No, stop, please don't." It's hot for her and for me.
Remember, this is all about consent. No means no, but "no" can be different words if that's what we agree to use.
Previously, I mentioned actions. We engaged in play where she's not going to be able to speak--breath play, tape gags, mouth fucking, etc. She can't always say her safe phrase. In our contract (and you do NOT need a contract; many submissives do like clearly defined rules, though, so it's something to consider), it says for her to tap three times OR make three noises in rapid succession: "Mmm mmm mmm." Either way, I know to stop.
Also, remember that with experience, a good Dominant knows how to read expressions, listen for changes in breathing, and take all kinds of physical cues that let them know that a submissive is in distress. After 28 years in the lifestyle, I have become very good at learning the subtleties--and overt signs, of course--that mean my partner is in distress. However, nobody is perfect, and people get carried away. Safe words are a must!
People can use all different safe words. It doesn't matter which words you use. It does matter that you clearly agree on them and that play absolutely stops when they are uttered, or if the actions or noises you agreed to make are taken or uttered. And play can stop for ANY REASON. It doesn't matter what it is. If you don't stop play, you are committing the crime of sexual assault.
