by chance （= accidentally， by accident）
偶然 considerate （=thoughtful of the needs ）
体贴的，考虑他人需要的，considerable
相当大的，值得考虑的 consist of
accidental [fortuitous] phenomena;
偶然现象
accident; a chance event;
偶然事件
an occasional cause;
偶然原因
run into an old acquaintance; meet an old friend by chance; come across an old friend;
偶然遇见一个老朋友
an incidental acquaintance;
偶然相识的人
The occurrence of such things is by no means fortuitous.
出现这种问题绝不是偶然的。
I struck upon that antique in a little shop in London.
我在伦敦一家小店里偶然发现那件古物。
