“食言”，指对自己说过的话不进行履行，形容说话不算数，不守信用（break one's promise），可以翻译为“go back on one's word”，表示“to not do something one said one would do；to renege on something”。

例句：

如果他答应帮忙，他就不会食言。

If he promised to help, he will not go back on his word.

他答应把书留给我之后，却食言而把它卖给了别人。

After promising to keep the book for me, he broke his word and sold it to someone else.