In short

A temporal clause pins one event to another in time — when I get up, before I sleep, after we ate, until the rain stops. Hebrew builds these with a small kit of subordinators that almost all end in ש־ (she-) and take a full, finite verb: כש־ (kshe-, “when”), לפני ש־ (lifnei she-, “before”), אחרי ש־ (aharei she-, “after”), עד ש־ (ad she-, “until”), מאז ש־ (me’az she-, “since”), and a few more. The ש־ is the same subordinating tie you already met building causal and purpose clauses; here it hooks a time clause onto the main sentence.

One rule carries the whole lesson: Hebrew keeps the real tense. English freezes the verb after “when” into the present even for a future event (“when I arrive tomorrow, I’ll call”). Hebrew does not — if the event is still to come, the verb is genuinely in the future: כשאגיע מחר אתקשר אליך (kshe-agia machar etkasher elecha). Getting that reflex right is most of what this lesson is for.

The rule

• A temporal clause carries a finite verb, tied on with ש־. Each of these subordinators introduces a whole clause — subject and a conjugated (past / present / future) verb — not a bare noun. The glue that lets a preposition like לפני (“before”) govern a clause instead of a noun is ש־: לפני שאני הולך לישון (lifnei she-ani holech lishon, “before I go to sleep”). Leave the ש out and you no longer have a clause link — just a stranded preposition.

• Keep the real tense — the future stays future. This is the load-bearing point. The tense inside the temporal clause matches when the event actually happens, exactly as in the main clause. Habitual/general → present: כשאני קם בבוקר (kshe-ani kam ba-boker, “when I get up in the morning”). Past → past: כשהייתי ילד (kshe-hayiti yeled, “when I was a child”). Future → future: כשאגיע לתל אביב (kshe-agia le-tel aviv, “when I get to Tel Aviv”). English says “when I arrive” with a present verb, but Hebrew refuses the present here — the arriving hasn’t happened, so the verb is future אגיע, never present מגיע.

• כש־ “when” is a prefix; כאשר is its literary twin. In everyday speech “when” is כש־, glued directly onto the following word with no space, just like ב־/ל־/ה־: כשהאוטובוס מגיע (kshe-ha-otobus magia, “when the bus arrives”). In writing and formal speech you will also meet the free-standing word כאשר (ka’asher) with the same meaning: כאשר יגיע הקיץ (ka’asher yagia ha-kayitz, “when summer comes”). Recognise כאשר in text; say כש in conversation.

• לפני ש־ “before” and אחרי ש־ “after” — and don’t confuse them with the bare prepositions. לפני and אחרי are prepositions in front of a noun (לפני הארוחה, lifnei ha-arucha, “before the meal”; אחרי השיעור, aharei ha-shiur, “after the lesson”). To put a whole clause after them, add ש־: לפני שאכלנו (lifnei she-achalnu, “before we ate”), אחרי שסיימנו (aharei she-siyamnu, “after we finished”). Noun → no ש; verb-clause → ש.

• עד ש־ “until” takes the future for a not-yet event. Waiting until something happens means that something is still ahead, so its verb is future: נחכה עד שהגשם ייפסק (nechake ad she-ha-geshem yipasek, “we’ll wait until the rain stops”). Here too English’s present (“until it stops”) must become Hebrew future ייפסק. Before a noun, use bare עד: עד מחר (ad machar, “until tomorrow”).

• מאז ש־ “since” anchors to a past starting point. Because “since” measures from a moment already past, its clause usually carries a past verb, while the main clause stays present: מאז שעברתי לירושלים אני מרגיש טוב (me’az she-avarti li-yerushalayim ani margish tov, “since I moved to Jerusalem I feel good”). Before a noun: מאז אתמול (me’az etmol, “since yesterday”).

• “While” = בזמן ש־ or תוך כדי ש־ (simultaneity). For two things going on at once, use בזמן ש־ (bizman she-) or the more “in the very act of” תוך כדי ש־ (toch kdei she-): בזמן שאתה מדבר בטלפון אני מבשל (bizman she-ata medaber ba-telefon ani mevashel, “while you’re on the phone I’m cooking”).

• ברגע ש־ = “the moment (that)”. A sharp, punctual “as soon as”: ברגע שראיתי אותה הבנתי (berega she-ra’iti ota hevanti, “the moment I saw her I understood”).

• כל עוד “as long as” takes NO ש. This one breaks the pattern: כל עוד (kol od) already introduces its clause by itself, so you do not add ש: כל עוד יש אור אפשר לקרוא (kol od yesh or efshar likro, “as long as there’s light one can read”). Likewise the literary כאשר takes no ש.

Forms & patterns

The temporal subordinators (each introduces a finite clause):

Preposition (+ noun) vs conjunction (+ clause) — same word, ש makes the difference:

Real tense after כש־ — the tense tracks the actual time (contrast English):

Examples

Common mistakes

• כשאני מגיע מחר, אתקשר אליך -> כשאגיע מחר, אתקשר אליך (kshe-agia machar, etkasher elecha) - a future event after כש takes the future אגיע; don’t copy English’s present “when I arrive”.
• לפני אני הולך לישון -> לפני שאני הולך לישון (lifnei she-ani holech lishon) - a finite clause after לפני needs ש; without it you have only the bare preposition.
• נחכה עד שהגשם נפסק -> נחכה עד שהגשם ייפסק (nechake ad she-ha-geshem yipasek) - the rain hasn’t stopped yet, so עד ש takes the future ייפסק, not the present נפסק.
• כש האוטובוס הגיע -> כשהאוטובוס הגיע (kshe-ha-otobus higia) - כש is a prefix; glue it onto the next word, never leave a space.
• אחרי אכלנו יצאנו -> אחרי שאכלנו יצאנו (aharei she-achalnu yatzanu) - “after” before a verb-clause is אחרי ש, not bare אחרי.
• לפני שהארוחה (meaning just “before the meal”) -> לפני הארוחה (lifnei ha-arucha) - before a plain noun use bare לפני; the ש appears only before a full verb-clause.
• כל עוד שאתה כאן -> כל עוד אתה כאן (kol od ata kan) - כל עוד introduces its clause on its own; it takes no ש.

Tips

• The one reflex to drill: keep the real tense. If the event is still to come, its verb is future — כשאגיע, עד ש…ייפסק — even where English uses the present.
• Almost every temporal connector here is “preposition + ש” (לפני ש, אחרי ש, עד ש, מאז ש, ברגע ש). Strip the ש and you’re back to the preposition, which then wants a noun, not a verb.
• Two exceptions to memorise: כאשר (one free literary word) and כל עוד both introduce a clause with no ש.
• כש־ glues on like ב־/ל־/ה־. If your finger reached for the spacebar, it’s wrong: כשהאוטובוס, not כש האוטובוס.
• “Before/after a noun” → bare לפני/אחרי (לפני הארוחה). “Before/after something happens” → לפני ש/אחרי ש + a verb.
• To say “before eating” as an event-noun (לפני האכילה) instead of a clause, Hebrew uses the action-noun; that’s the verbal-noun lesson. Here we always keep a full, finite verb.
• Colloquial Hebrew leans almost entirely on כש; reserve כאשר for writing and formal speech (see the register lesson).