Uses of the Plain (Dictionary) Form

Beginners are often told the plain (dictionary) form is "the casual version" — the way you talk to friends instead of using ます. That is true, but it badly undersells the form. The plain form is also grammatically load-bearing: it is the mandatory base that a large family of structures attaches to, and those structures appear in the most formal Japanese imaginable. 行くと思います ("I think I'll go") is polite — yet the embedded verb 行く is plain. Skipping the plain form because "I only need polite speech" is therefore impossible: you hit it at your very first embedded clause.

The core sentence shape: plain inside, polite at the end

Here is the single most important structural insight on this page. In Japanese, politeness lives on the final verb of the sentence, and only there. Any verb buried inside a clause — inside a quotation, a relative clause, or a grammar pattern — stays in the plain form regardless of how polite the whole sentence is. So the default shape of a polite complex sentence is:

[ … plain verb … ] + pattern + polite final verb

Master that shape and a huge amount of Japanese sentence structure falls into place at once.

Here 行く is plain (inside the と-clause) while 思います is polite (the sentence's final verb). That is the pattern in miniature.

〜と思う — "I think that …"

To report a thought, opinion, or guess, quote a plain-form clause with と and end with 思う ("think"). The quoted verb is always plain.

Note 来ない is the plain negative of 来る — negatives count as plain form too, so they slot in here just like affirmatives.

〜つもり — "I intend to …"

Attach つもり ("intention") to a plain non-past verb to say what you plan to do. つもり is a noun, so it takes だ / です to finish the sentence — and that final copula carries the politeness.

〜ことができる — "can / be able to …"

One way to say "can do X" is plain verb + ことができる (literally "the act of X-ing is possible"). The verb before こと is plain; できる at the end takes the politeness.

〜前に — "before …"

Plain verb + 前に means "before doing X." Even in a highly polite sentence, the verb in front of 前に stays plain — the politeness waits for the end.

Relative clauses — "the … that I …"

To modify a noun with a whole clause, put the plain-form verb directly in front of the noun — no relative pronoun, no "that/which." The modifying verb stays plain even when the main sentence is polite.

In both, the clause modifying the noun (私が作る → 料理; 彼女が住んでいる → 町) is plain, while the sentence ends politely with です. Same shape as always.

More patterns on the same plain base

The family is large. A few more you'll meet soon, all built on the plain form:

• 〜かもしれない ("might …"): 雨が降るかもしれません。
• 〜なら ("if / as for …-ing"): 京都へ行くなら…。
• 〜か（どうか） ("whether …"): 来るか分からない。
• 〜でしょう ("probably …"): 明日は晴れるでしょう。

Every one of these — かもしれない, なら, か, でしょう — clips onto a plain verb, and any politeness rides on the final element. Learn the plain form well and each new pattern is just "plain form + this."

How this differs from English

English marks tense and formality mostly on each verb independently, and it links clauses with words like "that," "to," and "which." Japanese instead keeps a strict division of labor: plain form does the internal grammatical work; the politeness marker (ます/です) is applied once, at the sentence's end. An English speaker's instinct is to make every verb "match" the sentence's politeness — to say ×行きますと思います because the sentence is polite. But in Japanese that over-politens an embedded verb that has no business being polite. The embedded clause is a self-contained plain unit; formality is a property of the sentence, stamped on its final verb, not of every verb inside it.

Common Mistakes

1. Politely conjugating the embedded verb. The verb before と, こと, 前に, つもり, なら stays plain — never ます.

2. Making the verb in a relative clause polite. A noun-modifying verb is plain, even in a polite sentence.

3. Using ます before 前に or つもり. These patterns demand the plain non-past.

4. Ending politely but forgetting the pattern needs a plain base for the copula's own clause. つもり/かもしれない take だ/です at the very end — the politeness goes there, not on the inner verb.

Key Takeaways

• The plain form isn't just "casual" — it's the mandatory grammatical base before 〜と思う, 〜つもり, 〜ことができる, 〜前に, 〜かもしれない, 〜なら, and it heads relative clauses.
• Master rule: plain inside, polite outside. Politeness is stamped once, on the sentence's final verb; every embedded verb stays plain.
• This holds even in formal speech — 行くと思います is polite overall but keeps 行く plain. Skipping the plain form is impossible; you meet it at your first embedded clause.
• The classic English-transfer error is over-politening the inner verb (×行きますと思います). Keep it plain: 行くと思います.