idem

[ahy-dem, id-em] /ˈaɪ dɛm, ˈɪd ɛm/
pronoun, adjective
1.
the same as previously given or mentioned.
Origin
1350-1400; Middle English < Latin īdem
Can be confused
ibid, ibidem, idem, op. cit.

alter idem

[ahl-ter ee-dem; English awl-ter ahy-dem, al-] /ˈɑl tɛr ˈi dɛm; English ˈɔl tər ˈaɪ dɛm, ˈæl-/
noun, Latin.
1.
another exactly the same.

semper idem

[sem-per ee-dem; English sem-per ahy-dem, id-em] /ˈsɛm pɛr ˈi dɛm; English ˈsɛm pər ˈaɪ dɛm, ˈɪd ɛm/
Latin.
1.
always the same.
British Dictionary definitions for idem

idem

/ˈaɪdɛm; ˈɪdɛm/
uknown
1.
the same: used to refer to an article, chapter, etc, previously cited
Word Origin and History for idem

Latin, literally "the same" (see identical).

semper idem

Latin, literally "always the same;" see semper- + identical.