"The big dog"
Translation:De grote hond
When the noun is being said with an indefinite pronoun (een + adjective + noun) you put -e at the end of the adjectives that qualify common gender words (de + noun) and, for the ones that qualify neuter gender words(het + noun), the adjective does not decline. However, if you're speaking with a definite pronoun (de or het), the adjectives always become declined.
So, knowing that meisje is neuter (het meisje) and hond is common (de hond):
- Het kleine meisje (definite pronoun)
Een klein meisje (indefinite pronoun)
De kleine hond (definite pronoun)
- Een kleine hond (indefinite pronoun)
Although, if the adjective finds itself after the noun, it will always be undeclined:
Het meisje is klein
De hond is klein
In your case, "groot" is the undeclined version and "grote" the declined one.
Usually, when the adjective has two vowels (such as groot) the declined version consists in eliminating one of the "o"s and putting an "e" at the end (groot -- grote)
When the adjective is normal (does not have two vowels) the declined version is obtained simply by addind an "e" to the end of it (klein -- kleine)