In some analytic frameworks, such neo-classical prefixes are excluded from analyses of English derivation on the grounds that they are not analyzable according to a mostly synchronic (that is, relatively productive or easily recognizable and relating to present-day idioms) English (that is, "native") basis. Conceptualized thus, anglicized neo-classical English words such as "deceive" are not analyzed by Marchand as being composed of a prefix "de-" and a bound base "-ceive" but are rather analyzed as being composed of a single morpheme (although the Latin sources of these English words are analyzed as such, as "native" Latin components in the Latin language). Similarly, pairs such as "defend/defense" and "double (or duple)/duplicity" are not considered morphologically related in Marchand's treatment of English word formation and are thus excluded too, though they are regarded as derivatives of the shared roots in Jespersen's and Koizul's, while in others, they may be seen as allomorphs or variants (like "deep/depth", a pair formed of Germanic components). However, not all foreign words are unanalyzable according to such an English basis: some foreign elements have been nativized and have become a part of productive English word-formation processes. An example of such a now native English prefix is "co-" as in "co-worker", which is ultimately derived from the Latin prefix "com-" (with its allomorphs "co-", "col-", "con-", and "cor-"); and "ex-" as in "ex-soldier", which derives from the Latin "ex-".