Confusion on expressing "want".

Hello all,
I'm here with another question that is leaving me a bit confused.

Through my initial study (via class and textbook), I thought that expressing "want" in the context of wanting to do something, was as easy as following the X が verb stem+たいです。Moreover, I thought that asking someone if they want to do something, would be as easy as adding か to the end of the sentence (i.e.映画が見たいですか).

Today I watched a video by a Japanese woman who teaches Japanese on her Youtube channel (Miku Real Japanese). She stated that using たい form to ask if someone wants to do something would be awkward among friends (using plain form) and very impolite when talking to superiors (as far as Keigo is concerned). According to Miku, たい can only be used to ask a question (regarding "wanting to do something") if it is used with an interrogative ( i.e どこに行きたいだ?) however, if asking your friend if they want to do something more generally, you would just use the plain form of the verb with a rising inflection, such as (食べる？-Do you want to eat?/ 来る？- Do you want to come?[to the event])

She also stated that when asking someone of a higher station if they want to do something, that you should use 〜いかがですか。Instead of verb+たいですか。(i.e. お茶はいかがですか).

I don't doubt Miku at all, however I'm wondering if this is true for all instances? What if, for example, you wanted to ask a co-worker of equal standing if they wanted to go to a coffee shop for lunch? Would 喫茶店で昼ご飯を食べたいですか be appropriate in this context? Also, is たい form still appropriate when stating that you want something to a superior? Is there another more respectful way state that you want something? For instance, is there any way to soften a sentence like: "あの会合が出席したいです."Which sounds fairly demanding.

Thanks for the help and the input.

烏天狗

Beginners aren't expected to use Japanese as effortlessly as two Japanese friends meeting each other, so I might keep that in mind when learning from Miku-sensei. (Her advice isn't wrong, but understand that its also OK for beginners to be somewhat unaware of all the nuances of Japanese).

If you are ready to consider yourself less of a beginner and more in the "intermediate" range (or, if you aspire to be in the intermediate range) then yes its good to learn some more situationally appropriate ways to express yourself. 「今日 映画を見に行きましょうか？」 or 「今日の会議に出席してもいいですか」, etc...

Expressing something as "I want" (verb stem+たい) can sound very direct, and being direct, as you know, can come across as demanding or somehow abrupt. This is useful if your intention is to be direct, clear, straightforward, but if you want to soften your speech in the right situations, you can express your desires in a more roundabout way using a number of other patterns - like the ones above or other variations.

烏天狗 said:

どこに行きたいだ?

Click to expand...

BTW you would never use だ. It's an adjectival form so it's a complete sentence without the copula.

烏天狗 said:

Would 喫茶店で昼ご飯を食べたいですか be appropriate in this context? Also, is たい form still appropriate when stating that you want something to a superior? Is there another more respectful way state that you want something? For instance, is there any way to soften a sentence like: "あの会合が出席したいです."

Click to expand...

Unfortunately the たい form is almost never used this way. Basic rule of thumb is to use it only for yourself. どう is casual equivalent of いかが
喫茶店で昼ご飯を食べたいですか
for this I might say
喫茶店で昼ご飯を食べたらどうですか
or more simply
喫茶店で昼ご飯はどうですか

For requests to a superior usually you would phrase it as a request for permission like Majestic said. Not state your own desire outright.

Also bonus pattern for you. When you want to state the desire of a third party you can use たい+がる.
烏天狗くんは喫茶店で昼ご飯を食べたがっている。

Thank you both for replying so quickly.

Your answers have both been very helpful and I feel like I can make more sense of these important distinctions of how to express "want" or to ask if someone else would want to do something in more appropriate ways.

I am trying, as Majestic put it, to elevate myself from a Beginner to an Intermediate speaker, so this is all very helpful.

I also appreciate the correction, as sometimes you don't know what you are doing wrong until its brought to your attention.

I do have a follow up question for you mdchachi, if you don't mind.

mdchachi said:

for this I might say
喫茶店で昼ご飯を食べたらどうですか

Click to expand...

In this case, what is the function of the conditional たら form of たべる?

Is it the equivalent of "if" in this context? i.e. "How would you feel IF we ate lunch at the coffee shop?"

Yes, that's the idea.

烏天狗 said:

I thought that expressing "want" in the context of wanting to do something

Click to expand...

If there's one piece of advice I'd give you, it's to try to break the habit of thinking of Japanese as a having 1-to-1 (or even a 1-to-0.999) correlation with English as soon as you can.

What I mean by this is: just because the ～たい form might be used to express "want" in the sense of expressing one's own desire, it doesn't mean it corresponds to all cases where we use "want" in English.

When you think about it, an expression like "Do you want to go see a movie on Saturday?" isn't really asking the other person "Do you (currently) have a desire to see a movie on Saturday?" at all. On the contrary, the idea of seeing a movie might not have even occurred to the other person until you mentioned it. Beneath the surface, it's actually just a way of extending an invitation, and we just happen to use "want" to express this in English.

In Japanese, this is expressed in other ways (as Majestic and mdchachi have explained in detail). In addition to the phrases they gave you, I'd also like to point out that one of the most common ways to extend an invitation is with the negative verb form.

今度の土曜日、映画（を）観に行きませんか？(polite です／ます form)
今度の土曜日、映画（を）観に行かない？(casual plain form)
(*I put the を in parentheses since it's often dropped in colloquial speech.)

You can think of this as equivalent to "Won't you go see a movie (with me)?" if it helps you make the connection, but in general, you shouldn't try to force Japanese grammar to conform to your understanding of how things work in English. I would say that an important hurdle to get over if you want to progress from the beginner to intermediate level is to not think in terms of "How do I say 'want' (or 'would', or 'can') in Japanese?", but rather "I'm trying to express [this sentiment] in [this situation]. How do I do this in (natural) Japanese?"

As an illustration of this, "I can speak Japanese." and "Can I borrow a pen?" both contain the word "can" in English, but they would be expressed in Japanese using completely different structures. You have to be able to process it not as "How do I express 'can' in Japanese?" but rather in terms of "expressing ability" and "asking for permission", and learning the appropriate Japanese phrases for each.

I realize that my commentary has gotten a bit philosophical here, but I believe this is an important concept to understand. (It's definitely one my Japanese teachers impressed upon me back in the day, and one I always tried to help my students understand back when I was a grad student teaching the language.)

At any rate, questions on this and other topics are always welcome here. Good luck with your studies!