Pa'al פ״י: ישב, ידע, ירד, יצא | Hebrew Grammar

פ״י is the class of pa'al roots beginning with י, and it contains "sit", "know", "go down", "go out", "give birth" and "sleep" — so you meet לָדַעַת and לָצֵאת long before anyone tells you the class has a name. It is also the class most often taught as one thing when it is really two, which is why its paradigm looks arbitrary in most textbooks. Separate the two and almost nothing has to be memorised.

Subclass 1: the yod disappears

This is the large group, and its behaviour is completely uniform. Past and present are regular; the future replaces the yod with a tsere in the prefix, and the infinitive is built on a לָ־־ֶ־ֶת shape with no yod anywhere.

Root	Past	Present	Future 3 m.sg	Infinitive
י־שׁ־ב sit	יָשַׁב yasháv	יוֹשֵׁב yoshév	יֵשֵׁב yeshév	לָשֶׁבֶת lashévet
י־ר־ד go down	יָרַד yarád	יוֹרֵד yoréd	יֵרֵד yeréd	לָרֶדֶת larédet
י־ד־ע know	יָדַע yadá	יוֹדֵעַ yodéa	יֵדַע yedá	לָדַעַת ladá'at
י־ל־ד give birth	יָלַד yalád	יוֹלֵד yoléd	יֵלֵד yeléd	לָלֶדֶת lalédet
י־צ־א go out	יָצָא yatsá	יוֹצֵא yotsé	יֵצֵא yetsé	לָצֵאת latsét

Three observations before the exceptions. ידע takes a patach where the others take a tsere — יֵדַע, not yedé — because its third radical is a ע, which is the third-radical guttural rule doing its ordinary job on top of this one; the same ע puts the furtive patach into לָדַעַת ladá'at and יוֹדֵעַ yodéa. יצא is doubly weak: י־צ־א is פ״י and ל״א, which is why its infinitive is לָצֵאת rather than a לָ־־ֶ־ֶת form. And the imperatives are short and genuinely current: שֵׁב shev, רֵד red, צֵא tse — and דַּע da, which survives mostly inside the set phrase דע לך da lekhá, "just so you know".

אנחנו יושבים בחוץ, בוא.

anákhnu yoshvím bakhúts, bo

We're sitting outside — come on over. (informal, to a man)

שב, אני מביא לך קפה.

shev, aní meví lekhá kafé

Have a seat, I'll bring you a coffee. (to a man)

אני לא יודעת מה לעשות עם זה.

aní lo yodá'at ma la'asót im ze

I have no idea what to do with this. (f. speaker)

ירדתי בתחנה הקודמת בטעות.

yarádti batakhaná hakodémet beta'út

I got off at the previous stop by mistake.

Where the yod went

The yod did not vanish — it was never a yod. These roots began with a ו in Proto-Semitic, and Hebrew turned every word-initial w into y. So the past tense יָשַׁב shows the changed letter, while the forms where the first radical is not word-initial preserve the original:

Root	pa'al — looks like a yod	hif'il and derived nouns — the ו is back
י־שׁ־ב	יָשַׁב · יֵשֵׁב	לְהוֹשִׁיב lehoshív to seat · מוֹשָׁב mosháv
י־ר־ד	יָרַד · יֵרֵד	לְהוֹרִיד lehoríd to take down

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That ו is also what the future's tsere is made of. The old prefix and the ו contracted into a single long e, which is why יֵשֵׁב has a vowel where a regular verb has a consonant: יִכְתּוֹב has three root letters visible, יֵשֵׁב has two. Nothing was deleted — one letter turned into the vowel you can hear.

Subclass 2: the yod stays, and doubles on the page

A much smaller group has a genuine yod, and it behaves quite differently: the yod survives into the future as part of a long i, which ktiv male then writes with a second yod.

Root	Past	Present	Future 3 m.sg	Written	Infinitive
י־שׁ־ן sleep	יָשַׁן yashán	יָשֵׁן yashén	יִישַׁן yishán	יישן	לִישׁוֹן · לישון
י־ב־שׁ dry out	יָבַשׁ yavásh	יָבֵשׁ yavésh	יִיבַשׁ yivásh	ייבש	לִיבֹשׁ · ליבוש

Notice that the present is different too. It is not יוֹשֵׁן but יָשֵׁן, the קָטֵל shape that doubles as an adjective — yashén means both "sleeps" and "asleep". That belongs to the stative pa'al verbs, which is also where the three different readings of unpointed ישן are sorted out.

ישנתי רק ארבע שעות והראש שלי מתפוצץ.

yashánti rak árba sha'ót veharósh shelí mitpotséts

I only slept four hours and my head is splitting.

אני הולכת לישון, נהיה מאוחר.

aní holékhet lishón, nihyé me'ukhár

I'm going to bed — it's getting late. (f. speaker)

הכביסה עוד לא יבשה.

hakvisá od lo yavshá

The laundry still isn't dry.

The trap: in ktiv male the future looks like the past

This is the practical hazard of subclass 1, and it is worth more attention than the paradigm. Israeli spelling writes the tsere of יֵצֵא with nothing at all — a single yod, the prefix. So the future and the past come out as the same string:

Written	Could be	or
יצא	יָצָא yatsá — he went out	יֵצֵא yetsé — he will go out
ירד	יָרַד yarád — he went down	יֵרֵד yeréd — he will go down
ישב	יָשַׁב yasháv — he sat	יֵשֵׁב yeshév — he will sit
יצאו	יָצְאוּ yats'ú — they went out	יֵצְאוּ yets'ú — they will go out

Only context tells you which — a time word, a preceding verb, the drift of the paragraph. And this is precisely where the two subclasses part company on the page: יישן has two yods and can only be a future, because subclass 2 keeps a real yod that ktiv male has to write. Seeing one yod or two on these verbs is genuinely informative.

בוא נצא מוקדם, יש פקקים.

bo netsé mukdám, yesh pkakím

Let's leave early, there's traffic. (informal, to a man)

אני יוצא לחמש דקות, כבר חוזר.

aní yotsé lekhamésh dakót, kvar khozér

I'm stepping out for five minutes, back soon. (m. speaker)

תרד רגע, אני מחכה למטה.

teréd réga, aní mekhaké lemáta

Come down for a second, I'm waiting downstairs. (informal, to a man)

אני אשב פה, זה בסדר.

aní eshév po, ze beséder

I'll sit here, it's fine.

Two verbs that behave as though they belonged here

הלך has a ה, not a yod, and conjugates exactly like subclass 1 anyway: יֵלֵךְ yelékh, אֵלֵךְ elékh, לָלֶכֶת lalékhet, imperative לֵךְ lekh. Only its past and present betray the ה — הָלַךְ, הוֹלֵךְ. It has its own page.

לקח has a ל, and treats it as though it were a נ: the ל assimilates into the ק in the future, leaving a dagesh — יִקַּח yikákh, written ייקח — exactly the פ״נ behaviour. Its infinitive is לָקַחַת lakákhat and its imperative the very common קַח kakh.

קח, זה בשבילך.

kakh, ze bishvilkhá

Here, this is for you. (informal, to a man)

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Learn these two with the class, not against it. הלך and לקח are among the most frequent verbs in the language, and both of them borrow their shape from a גזרה they do not belong to. That is not an accident: the oldest and commonest verbs are exactly the ones with time to wear down, which is why the beginner's vocabulary and the "advanced" weak-root chapters keep colliding.

The same pattern across the other binyanim — לְהוֹשִׁיב and לְהוֹרִיד in hif'il among them — is on פ״י across the binyanim.

Common Mistakes

1. Building a regular future. The transfer error: three root letters go in, so three root letters should come out.

❌ ישב

yisháv

Incorrect as a future — the yod is not a consonant in the future. יֵשֵׁב is yeshév, with a tsere in the prefix and no yod sound at all. The same goes for יֵרֵד yeréd and יֵצֵא yetsé.

✅ הוא ישב ליד החלון, הוא תמיד יושב שם.

hu yeshév leyád hakhalón, hu tamíd yoshév sham

He'll sit by the window — he always sits there.

2. Making a לִ־ infinitive. לכתוב, לסגור, לשמור all start לִ־, and these do not.

❌ אני צריך לירד בתחנה הבאה

Incorrect — there is no such infinitive. Subclass 1 builds it on לָ־ with a ־ֶת ending: לרדת, larédet.

✅ אני צריך לרדת בתחנה הבאה.

aní tsaríkh larédet batakhaná haba'á

I need to get off at the next stop. (m. speaker)

3. Regularising לקח. Its ל looks like an ordinary root letter and behaves like a נ.

❌ אני אלקח את זה איתי

Incorrect — the ל assimilates into the ק: אני אקח את זה איתי, ekákh. The imperative is קח kakh, not ‘lekákh’.

✅ אני אקח את זה איתי, אין בעיה.

aní ekákh et ze ití, ein be'ayá

I'll take it with me, no problem.

4. Giving subclass 2 a subclass 1 present. יושב is learned first, and ישן gets dragged along.

❌ הילד יושן כבר שעתיים

Incorrect — ישן keeps its yod and takes the stative shape: הילד ישן כבר שעתיים, yashén. There is no form ‘yoshén’.

✅ הילד ישן כבר שעתיים, אל תעיר אותו.

hayéled yashén kvar she'atáyim, al ta'ír otó

The kid's been asleep for two hours — don't wake him. (to a man)

Key Takeaways

פ״י is two classes, and treating it as one is what makes the paradigm look random.
Subclass 1 (the large one) drops the yod: past and present are regular (יָשַׁב, יוֹשֵׁב), the future takes a tsere prefix (יֵשֵׁב, יֵרֵד, יֵדַע, יֵלֵד, יֵצֵא) and the infinitive is לָשֶׁבֶת, לָרֶדֶת, לָדַעַת, לָלֶדֶת, לָצֵאת.
The first radical was historically a ו, and it resurfaces in hif'il and in nouns: לְהוֹשִׁיב, לְהוֹרִיד, מוֹשָׁב.
Subclass 2 (small) keeps the yod, which ktiv male doubles: יָשַׁן → יִישַׁן / יישן, and its present is the stative יָשֵׁן, not yoshén.
The ktiv male trap: יצא, ירד and ישב are the same string for the past and the future. Only two yods (יישן) settle it on sight.
הלך conjugates as subclass 1 despite its ה (יֵלֵךְ, לָלֶכֶת), and לקח conjugates as פ״נ despite its ל (יִקַּח / ייקח, לָקַחַת, קַח).
Sit, know, go down, go out, give birth and sleep are all in this class, so you use it fluently long before you can name it.

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