ע״ו and ע״י (Hollow Roots) Across the Binyanim

A hollow root carries a ו or a י in its middle slot. In its characteristic short stem that radical is not realised as a consonant: its history is visible in the vowel between the other two radicals. ק־ו־ם gives kam, שׁ־י־ר gives shar. Most of this page follows from one structural fact — the stem has two consonants where a binyan expects three — and from the different ways the seven moulds cope with that.

Start with the fact that decides how much of this you have to learn. ע״ו and ע״י are different classes on different roots — ק־ו־ם and שׂ־י־ם are as distinct as any two roots in the language — and pa'al keeps them apart most transparently: לָקוּם with a u, לָשִׂים with an i. In the productive short-stem patterns, the letter on the page belongs to the mould rather than identifying the root. Polel writes a cholam ו for both classes (קוֹמֵם, שׁוֹרֵר from שׁ־י־ר), huf'al a shuruk ו (הוּקַם, הוּשַׂם from שׂ־י־ם), and hif'il neither radical at all, giving both classes a long i (הֵקִים, הֵבִין). The ordinary pi'el route described below is the important exception: כִּיוֵּון and קִיֵּים do preserve the root's own middle letter.

The grid, on ק־ו־ם

Read the ו down that column and it is a different creature in every block. One letter, four fates.

The pi'el slot, and the thing the textbooks get wrong

A hollow root cannot form an ordinary pi'el the usual way, because pi'el doubles the middle radical and the short stem has no middle consonant to double. One Hebrew solution is the פּוֹלֵל pattern: repeat the third radical and let the pattern supply a cholam between the two stem consonants. That is why קוֹמֵם has two מs and הִתְקוֹמֵם keeps its vav.

Now the qualifier, and it is a real one: the polel is not the only route. Some hollow roots build a perfectly ordinary pi'el instead, by treating the ו as a full consonant with a vowel of its own. כ־ו־ן is the clearest case: pi'el כִּיוֵּון kivén "aimed, directed", hitpa'el הִתְכַּוֵּון hitkavén "meant, intended" — neither of them a polel, and both among the commonest verbs you will use. So the rule to carry away is "the pi'el column of a hollow root will not look like מְדַבֵּר", not "it is always a polel".

This route is also the one place outside pa'al where the root's own middle letter still shows, for a plain reason: a radical with a vowel of its own is written as itself. כִּיוֵּון shows the ו of כ־ו־ן; a ע״י root sent the same way shows its י — Pealim roots לקיים lekayém "to uphold; to hold (an event)" as ק־י־ם.

nif'al: thin, and not on ק־ו־ם

Pealim lists no nif'al for ק־ו־ם — there is no לְהִיקּוֹם, and inventing one is the commonest way learners try to make a passive here. Hollow nif'als do exist on other roots, but the few useful items are lexical and do not share one prefix vowel:

• נָכוֹן nakhón (כ־ו־ן) — the rare verbal paradigm means "was prepared, was established"; in everyday Hebrew you meet the separately listed adjective "correct, true".
• נִידּוֹן nidón (ד־ו־ן) — "was discussed, was tried". This one is genuinely current in legal and journalistic writing.
• נָבוֹן navón (ב־י־ן) — an adjective, "wise, discerning", rather than a productive verb. It still makes the spelling point in one word: the middle radical is a י and the form is written with a ו.

That ו belongs to the mould, so a root with no use for it does not get one: Pealim heads the geminate ס־ב־ב as לְהִיסּוֹב, but its finite forms drop the vav — past נָסַב, present נָסָב, both nasáv.

Where the passive of a hollow verb is wanted in ordinary Hebrew, it is usually the huf'al that supplies it: הוּקַם, הוּכַן, הוּבָא.

The hif'il merge — and the third class inside it

Hif'il is the most conspicuous of the merges, because it is the one binyan that writes neither letter. Every hollow root, whichever it hides, lands on הֵ־ִי־ with a long i that belongs to no class:

Nothing in the hif'il paradigm identifies the class, which is why הֵבִין is ב־י־ן and not ב־ו־ן however often you see the second in a word list. And there is a third group in the same room: geminate roots take the identical prefix vowels, because they too have a two-consonant stem. ס־ב־ב gives הֵסֵב, with future יָסֵב, and ק־ל־ל gives הֵקֵל, with future יָקֵל. Those futures share the kamatz of יָקִים and יָבִין rather than the patach of יַסְבִּיר. So "a kamatz prefix means a hollow root" is one step too confident: it means a short stem, which may be hollow or geminate.

Stress does the work the letters cannot

In pa'al the masculine singular past and present are one form — הוא קם is both "he got up" and "he gets up" — and in the feminine singular the two tenses are spelled alike and separated by stress alone: past is מלעיל, present מלרע. The plurals do not collide, because the present has endings of its own: past קָמוּ against present קָמִים and קָמוֹת.

Common Mistakes

1. Keeping the yod in the huf'al. The long i belongs to the active hif'il stem, and huf'al has an a there.

2. Giving the pa'al an object. קם is intransitive in every register; putting something up is a different cell of the grid.

3. Dropping the polel's vav. With only two visible radicals it is tempting to build the hitpa'el straight onto them.

4. Confusing the pa'al future with the hif'il one. אָקוּם and אָקִים are one letter apart on the page and mean unrelated things.

Key Takeaways

• In a hollow root's characteristic short stem, the middle ו or י is not realised as a consonant, so the stem has only two consonants — and each binyan compensates differently.
• ק־ו־ם fills six of the seven: קָם · קוֹמֵם · קוֹמַם · הֵקִים · הוּקַם · הִתְקוֹמֵם. The gap is nif'al — there is no לְהִיקּוֹם.
• The pi'el and hitpa'el slots are usually taken by the polel / hitpolel shape, which repeats the third radical around a cholam: קוֹמֵם, הִתְקוֹמֵם, שׁוֹרֵר (whence מְשׁוֹרֵר "poet"). But not always — כ־ו־ן builds an ordinary pi'el, כִּיוֵּון, and hitpa'el הִתְכַּוֵּון. That route is also the only place outside pa'al where the root's own letter still shows.
• Hollow nif'als are thin and lexical, not one uniform נָ־וֹ־ paradigm: compare verbal נָכוֹן and current legal נִידּוֹן; נָבוֹן is now an adjective. The everyday passive of a hollow verb is usually the huf'al — הוּקַם, הוּכַן, הוּבָא.
• Pa'al keeps ע״ו and ע״י apart most transparently — לָקוּם against לָשִׂים. Polel and huf'al print the mould's ו, and hif'il prints neither radical (הֵקִים, הֵבִין). Ordinary pi'el is the exception: כִּיוֵּון and קִיֵּים preserve the root letter. When the form neutralises the contrast, look the root up.
• Geminate roots share hif'il's hollow prefix vowels: הֵסֵב, future יָסֵב; הֵקֵל, future יָקֵל. A kamatz prefix means a short stem, not specifically a hollow one.
• In pa'al the m.sg. past and present are identical (הוא בא), and in the feminine singular stress carries the tense: gára she lived / gará she lives. The plurals stay apart (קָמוּ / קָמִים).
• Two consonants with a long vowel between them ⇒ hollow, and ten of the commonest verbs in the language are built that way: קם, בא, שם, גר, רץ, שר, טס, מת, שב, דן. Running the other way, הֵבִין, הֵכִין, הֵבִיא, הֵקִים are hif'il, not pi'el — מֵבִין looks like מְדַבֵּר, but the infinitive settles it: לְהָבִין has ל plus ה where pi'el has a bare ל.