筆

In a sentence

• 彼は書道で筆を使って文字を書きます。

  He uses a brush to write characters in calligraphy.

  In this sentence, '筆' refers to a writing tool—a brush used in traditional calligraphy.

• 筆記試験で鉛筆やペンの代わりに筆を使用しても構いません。

  You are allowed to use a brush instead of pencils or pens in the written exam.

  Here, '筆' is mentioned as an alternative writing implement for a written test, emphasizing its functionality as a writing tool.

• 彼女は詩を書くのに悲しみの筆を持っていました。

  She wielded a brush of sadness to write poetry.

  In this case, '筆' is used metaphorically to describe the instrument of writing poetry, embodying the emotional intent of the writer.