The apple is red.
Ringo wa akai desu.
りんご
apple (topic)
は
topic marker
赤い
red
です。
polite “is”
In real life (guy speech):
Ringo, akai na.
りんご、
赤い
な。
Explanation: Basic “X is Y” sentence. りんご (ringo) = apple; は (wa) marks the topic; 赤い (akai) = red (i-adjective); です (desu) is the polite ending. Pattern: Noun は Adjective です. Guy speech often drops は/です and may end with な (rough/casual) instead of softer よ/ね.