SO

Those lucky enough to be in a romantic relationship use the acronym SO to refer to their "significant other." A person's significant other is their romantic partner. Notably, the term SO is gender-neutral, so it can be used to refer to a person's bf, gf, husband, wife, or other type of partner.

As you might expect, you're most likely to encounter the SO acronym when talking with someone who is part of a couple. Some couples refer to each other as SOs simply because they prefer the term to its alternatives, while others do so to avoid "defining" their relationship too early.

An abbreviation used in baseball statistics to count the number of strikeouts by a pitcher or batter.

The SO abbreviation is commonly used to measure a pitcher's efficiency along with his ERA, W, L, and CG. It also appears in a batter's statistics to measure how well he is hitting. The SO abbreviation can be used interchangeably with K to keep track of strikeouts.