to discover the meaning of information given in a secret or complicated way

Decoding the paintings is not difficult once you know what the component parts symbolize. 一旦明白了画中各部分的象征意义，也就不难搞清楚这幅画的含义了。

to understand the meaning of a word or phrase in a foreign language in the correct way

Grammatical information helps learners to decode sentences. 语法信息有助于学习者正确理解句子的含义。