偶然

In a sentence

• 我偶然在市场上遇到了老朋友。

  I happened to meet an old friend at the market.

  Here, "偶然" is used to indicate an incidental or unplanned occurrence.

• 这个发现完全是偶然的。

  This discovery was completely accidental.

  In this case, "偶然" describes the nature of the discovery as unintentional or by chance.

• 偶然的几次交谈，让他们成为了朋友。

  A few occasional conversations made them friends.

  Here, "偶然" indicates something happening infrequently or without a fixed pattern.