DF
Dominance factor
DF stands for "dominance factor," which is a score that some League of Legends (LoL) players use to evaluate their in-game performance. Players with a large number of kills and/or assists and a small number of deaths have a higher DF (and likely really helped their team), while those with a large number of deaths have a lower DF (meaning they let their team down).
At the end of each match, LoL shows players their numbers of kills, deaths, and assists. Players can then calculate their DF by plugging those stats into the following formula:
(2 x Kills) + Assists - (3 x Deaths) = DF
For example, a player with 10 kills, 3 deaths, and 1 assist (or 10/3/1) would have a DF of 12:
(2 x 10) + 1 - (3 x 3) = 12
On the other hand, a player with 2 kills, 5 deaths, and 0 assists (or 2/5/0) would have a DF of -11:
(2 x 2) + 0 - (3 x 5) = -11
DF is an alternative to LoL's Kills Deaths Assists (KDA) ratio, which is a more commonly used measure of in-game performance. Notably, DF seeks to assign players more credit for kills and more blame for deaths, while also accounting for support champs' typically high assist counts.
Example
Can you score under par in this golf terms quiz?
DF is an endearing acronym for engaged couples who like to dote on each other. Most people use it when online in forums or on social media when referring to their fiance.
An example of when you might see DF is when a woman captions a picture on Facebook of the flowers he gave her, "My DF surprised me at work with these beautiful flowers!" Or, you might see it in a post in an online forum about dating, romance, or marriage.
DF is just one of many "dear" acronyms. Others include DH, DW, DS, and DD.