Yes, south is a Scrabble word!

Adverb

1. In a southern direction

Adjective

1. Situated in or facing or moving toward or coming from the south

Noun

1. The region of the United States lying to the south of the Mason-Dixon line

2. The southern states that seceded from the United States in 1861

3. The cardinal compass point that is at 180 degrees

4. A location in the southern part of a country, region, or city

5. The direction corresponding to the southward cardinal compass point