Instructions: In the text below, click on the words that are considered informal vocabulary.

Batteries are used in a plenty of electronic things like smart phones, digital cameras, toys, etc. You can classify batteries into two categories primary and secondary. Primary batteries, which are a lot more common, turn chemical reactions into energy and can't be recharged. But a big trouble with primary batteries has to do with toxic chemicals that are bad for the environment. Nowadays, one way keep this from taking place is to use rechargeable secondary batteries. Despite the fact that secondary batteries don't have so big energy capacity, they have become a more and more popular option. Also, as the secondary batteries' price has gone down, their market shares have gone up in Finland.