plus sign (+):

plus sign (+) [1]: a symbol used, especially in phonological analysis, to mark the presence of a particular feature. For example, [+anterior] indicates that the segment referred to is classified as anterior (front). See minus sign (menos), exclamation point [3] (!). [Spanish: signo de más [1]]

plus sign (+) [2]: a symbol used, especially in phonological rules, to indicate a morpheme boundary. In most cases, this use is equivalent to the hyphen [1] (-), although sometimes a range of symbols (e.g., -, +, =, [2]) are used to indicate different types or strengths of morpheme boundaries. [Spanish: signo de más [2]]