かもしれない

1. Origins, structure, and basic meaning

• Structure: Attach かもしれない to an unconfirmed proposition to present it as a possibility.
• Basic usage: この古い写真は祖父が撮ったものかもしれない。 cautiously suggests that the grandfather may have taken the photograph.

2. Common pitfalls and similar expressions

• Connecting nouns and na-adjectives
  • Omit だ in 明日は休みかもしれない and この方法は便利かもしれない. A verb retains the appropriate plain form, as in 忘れたかもしれない.
• Where the negative belongs
  • 来ないかもしれない suggests the possibility of not coming, while 来たかもしれない suggests that someone may already have come. Separately from the ない inside かもしれない, the preceding clause determines the event's negation and tense.