Wording effect describes the possible effects on participants caused by the order of presented words or even the choice of the words themselves.
For example, in an experiment a participant is asked to choose a word from a list. A good experimenter would have a differing order of the words between participants and groups throughout the study to ensure the participants are not being affected or influenced by the order of the words or the first word on the list.
Another example could be a mood study in which participants are asked to memorize a list of words, try to write them down, and then do a mood survey. Although the words are supposed to be irrelevant in the study the experimenter inadvertently chose words like 'rage', 'fight', and 'aggression' to include on the list. A wording effect occurs and the participants' results are showing to be in aggressive and angry moods because they were influenced subconsciously by the aggression related words on the list. Neutral words like 'sofa' and 'book' would have been better choices.