infix notation

from the GNU version of the Collaborative International Dictionary of English.

• noun (Computers) A notation for commands or instructions in which the operator is inserted between the terms on which it operates. Contrasted with prefix notation and postfix notation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mathematics Notation where operators appear between operands, for example a+b

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a notation for forming mathematical expressions using parentheses and governed by rules of operator precedence; operators are dispersed among the operands