Questions & Answers about De achtste auto is erg groot.
Why does "eighth" end in -ste (achtste) instead of -de?
Most numbers from 2 to 19 add -de to make the ordinal number (like tweede, vierde, vijfde). However, acht (eight) is a special case. Because it already ends in a T sound, adding -de would be hard to say, so it takes -ste instead to become achtste.
Why is the word for big groot here, and not grote?
When an adjective comes after the verb (like "is" in this sentence), it never gets an extra -e at the end. We only add the -e when the adjective comes directly before the noun, like if we said de grote auto (the big car).
I thought erg meant "bad" or "terrible". Why does it mean "very" here?
You are right that erg can mean "bad" when used as a normal adjective. But when you put erg directly in front of another adjective (like groot), it acts as an adverb meaning "very". You could also use heel here to mean the exact same thing: De achtste auto is heel groot.