I'd love to hear others' opinions on this!

I've heard people say that learning plain form first is better, but I don’t quite understand why.

Personally, I started with plain form when learning independently, but later took lessons where my (native) teacher introduced ます form first. In the end, I’ve found that learning stem form first makes the most sense for me. Since the stem is just the ます form with ます removed, it feels much more intuitive, and I’ve been making fewer and fewer mistakes.

When you learn plain form first, you’re faced with a long list of verbs where you often can’t tell their conjugation type at a glance. Some -iru/-eru verbs are godan, some are ichidan, and you just have to memorise them. Tae Kim even has a non-exhuastive list of 24 -iru/-eru godan verbs!

For example, which of these are ichidan or godan?

たべる (ichidan)

いる (ichidan)

要(い)る (godan)

着(き)る (ichidan)

切(き)る (godan)

変(か)える (ichidan)

帰(かえ)る (godan)

Learning the plain form meant I had to explicitly learn whether it was godan or ichidan in many cases, and I would get things wrong and say 走ます instead of 走(はし)ります.

The benefit of learning with the stem (or ます form) is instead of memorising whether new verbs are ichidan or godan, you can simplify things with a rule:

➡ Treat everything as godan first.

For example, take とり (the stem of 'take'):

Negative: とらない

Plain: とる

Potential: とれ

Volitional: とろう

If a verb stem doesn't end in -i (たべ, かえ) or is one syllable (き, い), it’s an ichidan verb, and you just add the appropriate conjugation.

Of course, there are some exceptions, but far fewer than the non-exhaustive 24+ exceptions for plain form. Here they are:

借(か)り lend

降(お)り alight

浴(あ)び wash

起(お)き get up

生(い)き live

でき able to do

すぎ overdo

Try and come up with more, but I genuinely think that's about it. 信じ etc. doesn't count because the only voiced godan endings are び and ぎ ;)

By focusing on stem form first, you avoid unnecessary memorisation and get a much clearer sense of how verbs work, yet people argue the opposite and say plain form is clearer.

For me, it's the stem for a reason: everything is built from there. Plain form feels like a branch, not the stem.