In short

Arabic has no future tense. It has the imperfect you already know and two small markers you put in front of it, and that is the entire system: أَكْتُبُ “I write” becomes سَأَكْتُبُ or سَوْفَ أَكْتُبُ, “I will write”. Nothing inside the verb moves. The thirteen cells of lesson 14 are the same thirteen cells here, with a letter or a word bolted onto the front.

Two things have to be got right, and both are mechanical. سَـ is a prefix, so it is written stuck to the verb with no space at all; سَوْفَ is a free-standing word. And the verb keeps its indicative ending untouched - the ḍamma of سَأَكْتُبُ and the ن of سَيَكْتُبونَ sit exactly where they sat before, because these markers change the time of the verb and never its mood.

The rule

1. Both markers sit on the imperfect, and only on the imperfect. المُضارِع on its own is timeless enough to cover the present; put سَـ or سَوْفَ in front of it and it is pinned to future time. يَدْرُسُ “he studies / he is studying” → سَيَدْرُسُ / سَوْفَ يَدْرُسُ “he will study”. Neither marker may go anywhere near a past-tense verb: سَكَتَبَ is not “he will write”, it is not Arabic at all. If the verb in front of you is a ماضٍ, the future markers have nothing to attach to.

2. سَـ is a prefix. Write it joined. It behaves like the و of “and” and the بِـ of “with”: one letter, carrying a fatḥa, welded to the next word. سَأَذْهَبُ، سَتَكْتُبينَ، سَنَدْرُسُ، سَيَذْهَبونَ - never with a space, never on its own line, and nothing may be inserted between it and its verb. Traditional grammar calls it سينُ التَّنْفيسِ, “the س of expansion”, the idea being that it pushes the action out beyond the present moment. You do not need the name; you do need the habit of typing it as part of the word.

3. The two spellings worth pointing at. In the first person singular the prefix أَ of the verb keeps its hamza, seated on an alif, and the س simply leans against it: سَأَكْتُبُ، سَأَذْهَبُ، سَأَجْلِسُ. With the “he/they” prefix يَـ you get the very frequent shape سَيَـ: سَيَكْتُبُ، سَيَشْرَبُ، سَيَذْهَبونَ. And where the first person already begins with a madda because the root starts with a hamza - آكُلُ from أَكَلَ - the madda stays and the س leans on that: سَآكُلُ, not سَأَأْكُلُ.

4. سَوْفَ is a separate word, and it stands immediately before the verb. سَوْفَ أَذْهَبُ، سَوْفَ تَكْتُبينَ، سَوْفَ نَدْرُسُ. It is written apart, it never joins, and although it is a whole word it is not free to move around the sentence: it comes directly in front of the verb it marks, exactly where سَـ would have gone. أَذْهَبُ سَوْفَ إِلَى المَدْرَسَةِ is as wrong as putting “will” after the verb in English.

5. The mood does not change: the imperfect stays مَرْفوع. This is the point most learners get wrong, because they expect a marker in front of the verb to do something to the back of it. It does not. The five endingless cells keep their ḍamma - سَأَكْتُبُ، سَتَكْتُبُ، سَيَكْتُبُ، سَنَكْتُبُ - and the cells with an ending keep their ن: سَتَكْتُبينَ، سَيَكْتُبانِ، سَيَكْتُبونَ. So سَأَذْهَبَ and سَيَذْهَبوا are both errors. Later you will meet particles that really do reach into the verb and change its ending (lessons 33 and 35); سَـ and سَوْفَ are not among them, and it is worth registering the contrast now.

6. Choosing between them: mostly free, with a tilt. In modern usage the two are largely interchangeable, and in most sentences you may write either. The tilt is this: سَـ is the lighter, more ordinary marker and suits the near and the concrete - سَأَشْرَبُ القَهْوَةَ بَعْدَ قَليلٍ. سَوْفَ is heavier. It reads as more remote in time, or more formal, or more emphatic - a promise, a declaration, a headline, a plan for next year rather than for this afternoon. Newspapers and official statements use سَوْفَ freely; a text message to a friend will almost always use سَـ. When in doubt, use سَـ; it rarely sounds out of place, whereas a misplaced سَوْفَ can sound pompous.

What you may never do is use both. سَوْفَ سَأَذْهَبُ is not extra-future, it is a mistake - pick one marker and drop the other.

7. A plain imperfect plus a time word is already a future. Arabic does not insist on the marker. If the sentence contains a word that fixes the time, the bare مُضارِع is perfectly normal future: نَذْهَبُ إِلَى السّوقِ غَدًا “we are going to the market tomorrow”. This works just like the English present used for an arrangement (“we fly on Tuesday”). Adding سَـ is also fine and slightly more explicit; the difference is small. The useful time words for now:

• غَدًا tomorrow - note the ending: ـً, an accusative with tanwīn.
• بَعْدَ غَدٍ the day after tomorrow - بَعْدَ takes what follows in the genitive (lesson 20).
• بَعْدَ قَليلٍ in a little while; بَعْدَ ساعَةٍ in an hour.
• اللَّيْلَةَ tonight; قَريبًا soon.
• الأُسْبوعَ القادِمَ، الشَّهْرَ القادِمَ، السَّنَةَ القادِمَةَ - next week, next month, next year.

Notice the accusative on the ones that stand on their own - the fatḥa on غَدًا، اللَّيْلَةَ، الأُسْبوعَ القادِمَ is not random. Arabic puts a time expression that answers “when?” into the accusative case, and the adjective agrees with it there: الأُسْبوعَ القادِمَ, both words with a fatḥa. That is the ظَرْف of lesson 31; for now, learn these expressions as fixed blocks with the fatḥa built in, and resist the pull of the nominative (الأُسْبوعُ القادِمُ).

8. Negation is not done with لا. You have just learnt لا + المُضارِع for “does not” (lesson 23), and the natural move is to put it in front of a future: لا سَأَذْهَبُ. Arabic does not allow this. The future has a negator of its own, لَنْ, which replaces the marker entirely - لَنْ أَذْهَبَ “I will not go” - and it does change the ending of the verb. That is lesson 37, and you do not need it yet. What you need today is the rule in its practical form: a verb carrying سَـ or سَوْفَ is not negated - the two markers attach only to an affirmative verb. Say it in the affirmative, or wait for لَنْ.

9. What is deliberately not here. “It will be” and other future nominal sentences need the verb كانَ, which is lesson 32; until then keep your futures verbal. The combination كانَ سَيَفْعَلُ (“he was going to do”), and the particle قَدْ that shades a verb towards “may” or “has already”, are lesson 45. سَـ on a derived verb (سَيُسافِرُ، سَنَسْتَقْبِلُ) works exactly as it does here, but those stems are lessons 46-48, so the tables below stay with sound Form I verbs.

Forms & patterns

The seven persons you will use most, on the sound Form I verb ذَهَبَ - يَذْهَبُ. The two right-hand columns are the same verb with the same ending; only the marker differs.

The six cells left out above - the three duals, one further masculine plural (أَنْتُمْ), and the two feminine plurals - hold no surprises. The marker is added and the imperfect is untouched, ن and all:

The join itself, one line per prefix letter. Four ordinary cases and one that looks odd on paper:

Time expressions that carry a future on their own, or alongside the marker. Learn the ending as part of the phrase.

Examples

Common mistakes

• سَ أَذْهَبُ -> سَأَذْهَبُ - the س is a prefix, not a word. It is written joined to the verb, with no space, exactly like the و of عَطْف.
• سَوْفَ سَأَذْهَبُ -> سَوْفَ أَذْهَبُ (or سَأَذْهَبُ) - one marker per verb. Doubling them adds nothing and is simply ungrammatical.
• سَكَتَبَ -> سَيَكْتُبُ - the markers attach to the imperfect only. A past-tense verb cannot be turned into a future by prefixing anything to it.
• سَأَذْهَبَ -> سَأَذْهَبُ - the verb stays مَرْفوع. سَـ changes the time, never the mood, so the ḍamma is untouched.
• سَيَذْهَبوا -> سَيَذْهَبونَ - the ن of the indicative stays for the same reason. Dropping it belongs to lessons 33 and 40, not here.
• لا سَأَذْهَبُ -> لَنْ أَذْهَبَ - لا negates a plain present. A future is negated with لَنْ, which replaces the marker altogether (lesson 37).
• سَأَجْلِسُ غَدٌ -> سَأَجْلِسُ غَدًا - a time expression answering “when?” goes into the accusative, and the tanwīn is written ـً.
• سَأَذْهَبُ الأُسْبوعُ القادِمُ -> سَأَذْهَبُ الأُسْبوعَ القادِمَ - same rule with a two-word phrase: the noun takes the fatḥa and the adjective follows it.
• سَأَأْكُلُ -> سَآكُلُ - the first person of أَكَلَ is آكُلُ with a madda, and the س leans onto that; there is no second hamza to write.
• سَهِيَ تَذْهَبُ -> هِيَ سَتَذْهَبُ - the marker belongs to the verb, not to the sentence or to the pronoun in front of it.
• أَذْهَبُ سَوْفَ إِلَى المَكْتَبَةِ -> سَوْفَ أَذْهَبُ إِلَى المَكْتَبَةِ - سَوْفَ is a separate word but not a mobile one; it stands directly before its verb.

Tips

• Take any present-tense drill you have already done and run it again with سَـ on the front. That is literally the whole lesson: no new endings, no new stems, thirteen familiar forms.
• Say the marker and the verb as one word, سَنَدْرُسُ, not “سَ … نَدْرُسُ”. If you hear a pause in your own voice you will write a space in your own text.
• Default to سَـ. Keep سَوْفَ for when you want weight - a promise, a formal announcement, or something genuinely far off - and you will sound natural in both registers.
• The two shapes to over-practise are the first person and the third: سَأَـ and سَيَـ. Between them they cover most of what you will actually write.
• Learn غَدًا، اللَّيْلَةَ، الأُسْبوعَ القادِمَ with their fatḥas glued on, as single vocabulary items. You will meet the rule behind that ending in lesson 31 and it will already feel right.
• When reading unvocalized text, do not take every initial س for a future marker: سَمِعَ، سَأَلَ، سَيّارَة begin with a root س. Ask whether what follows is a recognisable imperfect - أ / ت / ي / ن plus a stem. If it is not, the س belongs to the word.
• Do not try to negate a future yet. Rephrase in the affirmative, or use a plain present with لا, until لَنْ arrives in lesson 37.
• Ignore, for now, every other way Arabic has of talking about the future - قَدْ, كانَ سَيَفْعَلُ, the participle used for an imminent action. Two markers and a time word will carry you through everything an A1 conversation needs.