くださる

1. Meaning and Usage
くださる means 'to give' and is used when the giver is of higher social standing than the receiver (the speaker or their family/group), or for out-group members (like customers) to show respect and social distance. It is the honorific counterpart to くれる.

2. Grammatical Structures

• Giving an Object: [Superior] が [Receiver] に [Object] を くださる。
  Example: 先生が（私に）本をくださいました。(The teacher gave me a book.) Note that 私に is usually omitted in natural speech.
• Requesting an Object: [Noun] を ください。
  Example: 水をください。(Please give me water.) This basic phrase uses the imperative form of くださる。
• Doing a Favor: て-form + くださる。
  Example: 教えてくださいました。(They were kind enough to teach me.)

Orthography Note (Kanji vs. Hiragana): When requesting a physical object (as a main verb), it is acceptable to use kanji (下さい). However, when attached to a て-form to request an action (as an auxiliary verb), official Japanese writing guidelines dictate it must be written in hiragana (ください).

3. Irregular Conjugation
くださる belongs to a special group of five honorific verbs (along with いらっしゃる, おっしゃる, なさる, and ござる) that have an irregular ます-form stem. Instead of the standard り ending, the り in the polite stem changes to い:

• Correct: くださいました
• Incorrect: ×くださりました (This is a common misconjugation and is grammatically incorrect)

Additionally, its imperative form is also irregular: instead of the standard u-verb imperative ending (くだされ), it becomes ください.

However, note that the て-form and た-form follow completely regular u-verb rules: くださって and くださった。

4. Formal Requests
Beyond the standard てください, you can use the more formal pattern お + ます-stem / ご + noun + ください (use お with native Japanese verbs and ご with Sino-Japanese suru-verbs). Here, ください is the imperative form of くださる, utilized within this pattern for public announcements and formal service settings.
Example: 少々お待ちください。(Please wait a moment.)

Another highly frequent and polite request form is 〜てくださいませんか (Won't you please ~? / Would you be so kind as to ~?). This negative question form is softer and more polite than a direct request.
Example: 手伝ってくださいませんか。(Would you be so kind as to help me?)

You can also make negative requests using ないでください ([Verb-nai form] + でください), meaning 'Please do not ~'.
Example: 忘れないでください。(Please do not forget.)

5. Important Restrictions and Contrasts

• Contrast with いただく: With くださる, the giver is the subject (が). With いただく, the receiver is the subject (が).
  Example: [Superior] が (私に) 教えてくださいました。(The superior kindly taught me.)
  Example: [私] が (Superior に) 教えていただきました。(I had the superior kindly teach me.)
• Third-Party Restriction: くださる is used when a superior gives something to the speaker's in-group OR to the listener (e.g., 先生が田中さんに本をくださいましたか？). It cannot be used for third-party to third-party giving.
• Uchi/Soto (In-group/Out-group) Rule: Never use くださる to describe an in-group superior (like your own boss or family member) giving you something when you are speaking to an out-group person (like a client). In such cases, use くれる instead to show humility to the outsider.