oct- en · X Meanings (form-of, morpheme) Form of octa- or octo- used before a vowel. form of octa- or octo- used before a vowel (morpheme) Used for the digit eight to form systematic element names of elements whose existence has been predicted, and which have not yet been given a trivial name. un- (“1”) + bi- (“2”) + oct- (“8”) + -ium (element suffix) → unbioctium (“element 128”) Relateds octette · -oct- · octuplet · octet · octad