This is a very simple icon that is meant to represent the plus sign used in addition. It's made of two lines of exactly the same size crossed over each other so that they run perpendicular. The lines are fairly thick.
This is a Plus Math icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,300 icons, all in the same style and quality.