No noun behind it, no ending on it
German adjectives behave differently in two places. In front of a noun (the big house) they take endings, which is a topic of its own. After the verb (the house is big) they take nothing: you use the plain dictionary form, whatever the gender or number of the subject.
One adjective form, four subjects
Das Haus ist groß.
The house is big.
Der Mann ist freundlich.
The man is friendly.
Die Suppe ist heiß.
The soup is hot.
Die Kinder sind müde.
The children are tired.
plural subject, and still nothing on the adjective
sein, werden, bleiben
sein names a quality (ist, sind), werden says it begins (wird, werden) and bleiben says it continues (bleibt, bleiben).
Mein Kaffee ist kalt.
My coffee is cold.
sein
Es wird dunkel.
It's getting dark.
werden
Ich werde krank.
I'm getting ill.
werden
Das Fenster bleibt offen.
The window stays open.
bleiben
English says get here: it's getting dark, she's getting tired. The German verb for that is werden, not bekommen (which means receive).
Giving an opinion with finden
To say what you think of something, use finden + the thing + a plain adjective. Germans do this all day, and the word order is the same as in English I find the film good.
Ich finde den Film gut.
I think the film is good.
Ich finde das Buch langweilig.
I find the book boring.
Turning it up or down
Words like sehr (very), ziemlich (fairly) and zu (too) stand directly in front of the adjective. They never change either.
Der Film ist sehr gut.
The film is very good.
Heute bin ich ziemlich müde.
Today I'm fairly tired.
Die Hose ist zu klein.
The trousers are too small.
The same word as an adverb
To say how someone does something, English adds -ly: she cooks well, he drives fast, he speaks loudly. German adds nothing: the plain adjective is also the adverb.
Das Essen ist gut.
The food is good.
adjective
Sie kocht gut.
She cooks well.
adverb, same form
Das Auto ist schnell.
The car is fast.
adjective
Er fährt schnell.
He drives fast.
adverb, same form
