The conventional wisdom is that when a child learns two languages, his acquisition of vocabulary will be slower than that of a monolingual child. But from my experience, there was at least one instance in which his knowledge of the English word helped him to remember the Chinese equivalent.

He must have previously learnt the word ‘colourful’ in school, which catalysed me to teach him a Chinese idiom ‘五颜六色’ that means ‘colourful’.
He applied his knowledge today by describing the balls at this indoor playground as 五颜六色. Okay, so these balls aren’t exactly colourful but I’m kinda relieved that the first idiom he acquires isn’t the ubiquitous 风和日丽 (sunny day) that I count this as a stellar learning moment.