Alterior or Ulterior: Which Is Correct?

The word that means hidden, concealed, or lying beyond what is openly stated, almost always in the phrase ulterior motive, is ulterior, beginning with a u. The version alterior is not a word: it appears in no dictionary and is always an error. The confusion arises because the idea of a hidden or secret motive connects naturally with words like alter, alternative, alias, and alibi, all beginning with al- and all suggesting something other, changed, or covered up. That association leads writers to swap the u for al and produce alterior motive. The meaning seems to fit, an ulterior motive is, after all, a different reason hidden behind the stated one, but the actual word is ulterior, from the Latin for further or beyond. An ulterior motive lies beyond the visible one. This places alterior vs ulterior among the commonly confused words where a plausible-sounding substitution produces a word the language never adopted. This guide explains what ulterior means, why alterior feels right, and a simple way to keep the u in place.

Which One Is Correct?

Ulterior is the correct word, and alterior is not an accepted word at all. Whenever you mean a hidden reason or concealed purpose, "he had an ulterior motive," "her interest was not ulterior," "ulterior aims", the word is ulterior, with a u. Writing alterior is an error, the equivalent of substituting a similar-sounding non-word for the real one, because alterior does not exist in standard English.

The reason lies in the word's origin. Ulterior comes from the Latin ulterior, meaning further, more distant, or beyond (the comparative of ulter, "on the far side"). In English it took on the figurative sense of lying beyond what is openly shown, hence hidden or concealed. So an ulterior motive is one that lies beyond, or behind, the motive a person admits to. The u and the ult- beginning are inherited directly from that Latin root.

The mistaken alterior has no such pedigree. It looks like it might be built on alter (Latin for other or to change), and that is exactly the false association that produces it, but no word alterior was ever formed. The real Latin family here is ult- (beyond), not alter- (other). Recognizing that ulterior belongs with ultimate and ultra, words about going beyond, rather than with alter and alternative, is the key to spelling it correctly.

What the Word Means

Ulterior is a fairly specialized adjective, used in modern English almost entirely in one phrase, but its meaning is worth unpacking because understanding it points straight to the spelling.

The central meaning is lying beyond or outside what is openly stated; hidden, concealed, kept from view. An ulterior purpose or motive is a real reason for an action that the person does not admit, one that sits behind the public, stated reason. "He offered to help, but he had an ulterior motive", he had a private, undisclosed reason, perhaps self-interest, that lay beyond his stated wish to be helpful. The word carries a faint sense of something concealed for advantage, so it often has a slightly suspicious or self-serving tone.

By far its most common use is the fixed collocation ulterior motive(s). This phrase is so dominant that ulterior rarely appears apart from it in everyday writing; when you reach for the word, it is almost always to say someone has an ulterior motive. Other pairings, ulterior purpose, ulterior aim, ulterior design, exist but are far less frequent.

There is also an older, more literal sense, situated beyond or more remote, and a sense of later or subsequent (as in ulterior developments), but these are rare and formal. For practical purposes, ulterior means hidden, beyond what is shown, and lives in the phrase ulterior motive. In none of these uses is alterior ever correct; the word is always ulterior, with its u and its ult- root signaling beyond.

Why People Write Alterior

If alterior is not a word, why does it turn up so readily? The cause is a strong, meaning-based association with a cluster of al- words that all suggest otherness or concealment.

The main driver is the pull of alter and alternative. An ulterior motive is, in plain terms, a different, other reason hidden behind the stated one, and the words alter (to change), alternative (another option), and alter ego (another self) all revolve around exactly that idea of otherness. Because the concept of "another, hidden reason" lines up so neatly with alter-, writers' minds supply the al- beginning, reshaping ulterior into alterior. The false form feels semantically justified, even though it is wrong.

A second factor is the reinforcing crowd of other al- words tied to concealment or deception: alias, alibi, allege. These hover around the same territory as a hidden motive, secret identities, cover stories, and they keep the al- sound primed, nudging the spelling further from the correct u.

A third factor is that ulterior is a comparatively uncommon, somewhat formal word that most people encounter only in the spoken phrase ulterior motive. Heard rather than read, and rarely written out, its exact spelling is not firmly fixed for many writers, so when they do put it on the page, the meaning-driven alterior substitutes easily. The cure is to break the false link with alter and forge the true one, with ultimate and ultra, so the ult- beginning, meaning beyond, comes to mind with the word.

Examples in Sentences

Seeing ulterior used correctly, with the alterior error corrected, fixes the right form.

Correct uses of ulterior:

• I suspected he had an ulterior motive for offering to drive me.
• Her generosity was genuine, with no ulterior aim.
• They questioned whether the donation had an ulterior purpose.
• Nothing he did seemed free of some ulterior design.

Correct related ult- words:

• This is our ultimate goal, beyond all the smaller ones.
• The race demanded ultra endurance.

Wrong → right corrections:

• She clearly had an alterior motive. → She clearly had an ulterior motive.
• His offer hid an alterior purpose. → His offer hid an ulterior purpose.
• There was nothing alterior about it. → There was nothing ulterior about it.

In every correction, the non-word alterior is replaced by ulterior, with its u. The meaning, a hidden reason lying beyond the stated one, is exactly what the ult- (beyond) root expresses.

Ulterior vs Alterior: Side by Side

The table sets the real word against the mistaken form and shows why they part ways.

Aspect	Ulterior (correct)	Alterior (incorrect)
Status	Standard English word	Non-word, not in dictionaries
Beginning	ulter- / ult- (u)	alter- (al)
Root meaning	Latin: further, beyond	mistakenly tied to alter, "other"
Related to	ultimate, ultra	(alter, alternative, but wrongly)
Common phrase	ulterior motive	none, always an error
In dictionaries?	Yes	No

The decisive row is the root: ulterior comes from Latin beyond and belongs with ultimate and ultra. Alterior mistakenly borrows the alter- of alter and alternative, which is not where this word comes from.

How to Remember

The cleanest trick is to tie ulterior to ultimate and ultra, all beginning with ult- and all carrying the sense of beyond or further. An ulterior motive lies beyond the one you can see, the ultimate, deeper reason, so the ult- beginning fits the meaning exactly. Picture ulterior, ultimate, and ultra together, and the u stays firmly in place.

A second guard is to consciously break the false link with alter. Yes, an ulterior motive is a "different" reason, but the word is not built on alter (other); it is built on ulter (beyond). When alterior tempts you, remind yourself that the hidden motive lies beyond the stated one, not merely alternative to it, and beyond points to ult-. Hold the phrase "an ulterior motive lies beyond" in mind, and the correct ulterior comes out every time. Between the ultimate/ultra family and the beyond logic, alterior loses its grip.

Related Spelling Mixups

Alterior vs ulterior belongs to a family of errors where a plausible-sounding substitution replaces the real word. If this one tripped you, two related cases are worth a look. The first is recognization vs recognition, where a regular-looking pattern produces a form English never adopted. The second is make do vs make due, where a meaning-based confusion swaps in the wrong word. Each, like ulterior, rewards knowing the word's actual root and meaning, rather than trusting a form that merely seems to fit the idea.

Conclusion

The word meaning hidden or concealed, lying beyond what is openly stated, is ulterior, and alterior is not a word, no dictionary lists it, and it is always an error. The mistake is a natural one: an ulterior motive is a different, secret reason behind the stated one, and that idea of otherness pulls writers toward alter, alternative, and alias, reshaping the word into alterior. But ulterior comes from the Latin for further or beyond, and it belongs with ultimate and ultra, not with alter. An ulterior motive lies beyond the visible one, which is exactly what the ult- root means. The reliable cure is to tie ulterior to ultimate and ultra, keep the meaning beyond in mind, and deliberately reject the false alter link. Do that, and you will write ulterior motive correctly every time. For more pairs where a plausible substitution replaces the real word, browse the full collection of commonly confused words.