Within linguistics, a pseudoword is defined specifically as respecting the phonotactic restrictions of a language. ^[1] That is, it does not include sounds or series of sounds that do not exist in that language: it is easily pronounceable for speakers of the language. When reading pseudowords, some cite the need to reflect on the real words that are "friendly" and "unfriendly". ^[2] For instance, "bave" can be read easily due to the number of its friendly words such as cave, pave, and wave. Also, when written down, a pseudoword does not include strings of characters that are not permissible in the spelling of the target language. "Vonk" is a pseudoword in English, while "dfhnxd" is not. The latter is an example of a nonword. Nonwords are contrasted with pseudowords in that they are not pronounceable and by that their spelling could not be the spelling of a real word.

Pseudowords are created in one of two ways. The first method involves changing at least one letter in a word. The second method uses various bigrams and trigrams and combines them. Both methods evaluate certain criteria to compare the pseudoword to another real word. The more that a given pseudoword matches a word in terms of criteria, the stronger the word is. ^[3]

Nonsense syllables were first introduced by Hermann Ebbinghaus ^[4] in his experiments on the learning of lists. His intention was that they would form a standard stimulus so that experiments would be reproducible. However, with increasing use it became apparent that different nonsense syllables were learned at very different rates, even when they had the same superficial structure. Glaze ^[5] introduced the concept of association value to describe these differences, which turned out to be reliable between people and situations. Since Glaze's time, experiments using nonsense syllables typically control association value in order to reduce variability in results between stimuli.

Nonsense syllables can vary in structure. The most used are the so-called CVC syllables, composed of a consonant, a vowel, and a consonant. These have the advantage that nearly all are pronounceable, that is, they fit the phonotactics of any language that uses closed syllables, such as English and German. They are often described as "CVC trigrams", reflecting their three-letter structure. Obviously many other structures are possible, and can be described on the same principles, e.g. VC, VCV, CVCV. But the CVC trigrams have been studied most intensively; for example, Glaze determined association values for 2019 of them. ^[5]