Hello!
So, I’ve recently come to learn that both verbs and adjectives are conjugated in Japanese.
Is there any specific rule as to when someone should conjugate the adjective in a sentence instead of the verb? Or does it have to be both?
For example,
今日は寒かったです
vs.
今日は寒いでした
Are these both proper? Are they both natural?
I feel like I’m just blanking on something super obvious here, but its not clicking for me.
Thank you!
First of all, です is not a verb it is a copula. It is a contracted form of であります where である is a verb. So, no, 寒いでした is not grammatical.
The first one is correct.
There are two groups of adjectives and they conjugate differently. This is usually covered fairly early on in most grammar texts - do you have one you are studying?
@anon79333215: copulas are a form of verb, so です is a verb.
Correct, copulas can be verbs, but not in the case of です. である is a verb. です is not. でした is also not an inflection of です it’s a contracted form of でありました.
Ok, one thing you need to understand is that in this sentence, です isn’t necessary. It’s only there to be polite. The confusing part is that です can also act as a copula and be a necessary, and grammatical, part of the sentence.
Is a perfectly valid sentence. So you have to watch out for when です is being use a polite sentence ender or performing a grammatical function.
See @anon79333215’s and @Rowena’s posts:
I think of です as just the polite form of だ when used as a copula, regardless of the origin. And Wiktionary lists でした as the past tense inflection of です, so there’s nothing technically wrong with the sentence.
Not reeeeeeally. 
It depends on what you’re saying. One thing to note is that the things that are called い-adjectives actually include the “to be” part. So, 赤い means “is-red” and not just “red”. 寒い means “is-cold”.
And that’s why you can conjugate them like that.
For so called な-adjectives, they’re really adjectival nouns so you have to add な in order to link them to something, and you then conjugate that な if necessary.
desu is believed to be a contraction of "de gozaimasu ", which is now mainly used in keigo (honorific speech). At some point, the negative forms of gozaimasu were also replaced by the negative forms of arimasu .
I haven’t made it too far into any texts. Most of my learning has been via JapanesePod101 and various youtube videos, with small doses of Tae Kim’s Guide.
There’s a good chance I’ve seen/heard this explained already and just forgot… haha.
Try watching Cure Dolly on YouTube. Her lessons are stellar, although the android voice and click-baity titles may take some getting used to.
Tae Kim is great as an intro, but it is a lot of info, so yes, you may need to go over it more than once for stuff to sink in. The main drawback of TK is that you don’t have exercises to apply what you’ve learned.
Fun fact: if the adjective is modifying a noun, then conjugating the adjective yields a slightly different sentence than conjugating the copula.
So, if we start with 今日は寒い日です = today is a cold day.
今日は寒かった日です = today was a cold day (but it’s not cold any more - it’s warmed up)
今日は寒い日でした = today was a cold day (but now it’s over, because it’s late evening)
Isn’t that 綺麗だった?
To my knowledge, な is a special form of だ that is used in… certain circumstances like if you want to continue the sentence maybe? (not a linguist 
)
So you say 綺麗だ and conjugate it to 綺麗だった but if you want to use it to describe something you need to say 綺麗だな人, same if you want to add the の or ん to it like 綺麗だなの or 綺麗だなんだ
EDIT ~なった sounds like a conjugated form of ~なる. 寒くなる => 寒くなった
Hey, I learned something new today. 
So, is 日 in that sentence pronounced ひ or か? Or にち?
Heck, maybe even じつ?
Although it can’t be じつ can it? Because wouldn’t that be 実? I think I’ve been doing WK too long, lol.
Ditto! Thanks Belthazar 
Aye, that’s correct. The post was getting long and I think I edited it like 3 times, so that was my mistake.
ひ. It’s only か when it’s functioning as a counter, and its one of those common-use words that use kun’yomi when they’re standing alone.
I’ve watched several of her videos. Somehow, her teaching style doesn’t resonate with me like it seems to for others.
Perhaps I’m just too new to grasp what she’s teaching, I dunno.
Yeah, it’s not for everybody. Have you watched Sambonjuku 三本塾? His videos are more traditional and they’re all in Japanese. Plus, he talks really clearly, so it’s easier to understand even with subtitles.
The premise of Cure Dolly is that there’s all these “secrets” that “they” won’t tell you about Japanese. In reality, it’s just that, traditionally, grammar education for non-natives is different from grammar education for natives. That’s true in any language. And so the explanations in the videos are basically telling non-natives about native-focused grammar education perspectives.
But, there are reasons why certain ways of framing things are used for non-natives. Generally speaking, the ways of explaining things to non-natives get you up and running with your very initial sentences and short conversations faster. It’s impossible to do a complete start from the native perspective anyway, but yeah.
It’s not that I think that thinking about the native style of grammar education is a bad thing. On the contrary, I find it very helpful. But it’s also not some kind of secret that Cure Dolly discovered or anything.
I think that’s why it resonates so much with people who already have some learning under their belt or have been struggling with Japanese for a while. It feels like the logical next step in understanding the language.
I completely agree. But I don’t know of any other source that’s readily available to fill in the gap between knowing enough to be able to understand native-focused education, albeit in English, and being able to use native materials.
Just subscribed and will take a look later. Thanks!