Last night I spoke quite a bit of Mandarin with some people from China, and while I was able to have a good conversation with them, though there were some things I couldn’t remember or didn’t know how to say. Usually when this happens I try to find another way to express the same idea, or if the people I’m talking to speak English, as was the case last night, I might say whatever it is in English and ask them how to say it in Mandarin. When they tell me, I often realise that I did know the words, but they just wouldn’t come to mind.
It’s likely that there’ll be gaps in your vocabulary, both in languages you’re learning, and in your native language, unless you memorise dictionaries. If the gaps are things you talk about frequently, it certainly helps to learn the words for them, but for other things you could use paraphrases. For example, one of the words that came up last night was pyramid. I didn’t know how to say it in Mandarin, but one of the Chinese guys did. After I got home I thought of a way to express the idea of a pyramid in Mandarin: 人造的小山,在埃及可看到的 (rénzhào de xiǎoshān, zài āijí kĕ kàndào de) – “man-made little hills that can be seen in Egypt” – not perfect perhaps, but it should get the message across.
In case you’re wondering, the Mandarin for pyramid is 金字塔 (jīnzìtǎ), which could be glossed as “tower shaped like the character 金”.