The seven pillars (arkan) of prayer

Saying "Allahu Akbar" at the start of the prayer is a pillar. You must say "Allah" clearly, without stretching it out strangely or adding extra letters, and say the "l" sound clearly; otherwise it doesn't count.

Standing is a pillar in every prayer except nafl prayers, which you can pray sitting even without a reason. You must stand long enough to recite at least a little Qur'an. If you truly cannot stand, because of sickness, old age, or another good reason, you may sit instead.

Reciting at least a little bit of the Qur'an in the prayer is a pillar, for anyone able to do it. You must pronounce the letters properly; someone who can but doesn't try, their prayer does not count. Someone who follows an imam should stay quiet during the imam's own recitation.

Bowing so your hands can reach your knees is a pillar in every rak'ah. You don't need to stay bowed for a long time; just bowing counts. Someone whose back is already bent should bow a little further, or nod with their head if they truly cannot bow at all.

Sujood means putting your forehead on the ground, and it happens twice in every rak'ah. Seven parts of your body must touch the ground: both feet, both knees, both hands, and your forehead (your nose should touch too; leaving it up is disliked without a real reason). If a wound or a real excuse stops your forehead touching, put your nose down instead; if neither can touch, just nod your head. The ground must be firm enough to support your forehead, and if it's raised, it must be no higher than about a hand's width.

Sitting after the two sajdahs of the very last rak'ah is a pillar. You must sit for at least as long as it takes to say the Tashahhud up to "...ʿabduhū wa rasūluh."

After finishing all the pillars, you must end the prayer with an action, usually by saying "As-salamu Alaikum", or by turning away from the Qibla, or by speaking.

Takbeer Tahreema, saying "Allahu Akbar" at the beginning of the prayer, is mandatory. "Allah" must not be drawn out or given an extra letter (as in "Al-lah"), "Akbar" must not be mispronounced, and the "lam" of "Allah" must be pronounced clearly, or the Takbeer is not valid.

Qiyam (standing) is obligatory in every prayer except Nafl, where sitting is permitted without any excuse. Standing must last long enough to recite at least one verse of the Qur'an; reciting Surah Al-Fatiha and a short Surah is necessary for this, and standing longer for a fuller recitation is preferable. Someone unable to stand, through illness, old age, or another valid reason (including being unable to cover the awrah while standing), may pray sitting.

Reciting at least one verse of the Qur'an, long or short, is mandatory for anyone able to do so. Recitation is obligatory only in the fard prayers' first two rak'ahs; in Witr, Sunnah and Nafl prayers it is required in every rak'ah. The recitation must pronounce the letters correctly; someone able to do this who does not is invalid, though someone with a genuine speech difficulty is exempt. A follower must stay silent during the Imam's recitation rather than reciting aloud.

Bowing in every rak'ah so that the hands reach the knees is obligatory; the forehead should be roughly level with where the knees are. Simply bowing is sufficient; staying bowed for a long time is not required. Someone whose back is naturally bent should indicate the bow further with the head.

Sujood, placing the forehead on the ground, occurs twice in every rak'ah. Seven body parts must touch the ground: both toes, both knees, both hands and the forehead (the nose should touch alongside it; placing only the forehead without the nose, without an excuse, is disliked). If placing the forehead is difficult due to an excuse such as a wound, the nose alone may be placed; without an excuse, sujood on the nose alone is not valid. If neither can touch, sujood is performed by gesture with the head. The surface must be firm enough to support the forehead, and if raised, it must be no more than about a hand-span above the level of the feet; higher than that, without a valid excuse, is not permitted. If a turban comes down so the forehead reaches the ground, sujood is valid through it; otherwise not. A second sujood performed before sitting up, or nearly sitting up, after the first does not count.

Qa'dah Akhira, sitting after both sujoods in the final rak'ah of the prayer, is obligatory, for long enough to recite At-Tahiyyat up to "...ʿabduhū wa rasūluh"; sitting longer than that is not required.

After completing all the pillars, it is obligatory to end the prayer with an action, such as saying "As-Salamu Alaikum," turning away from the Qiblah, or speaking.

The takbīrat al-taḥrīmah, pronouncing "Allāhu Akbar", inaugurates the prayer and is a rukn. "Allāh" must not be lengthened abnormally or given an inserted letter (as in a mispronounced "Ākbar"), and the lām of the name must be articulated distinctly, failing which the takbīr does not take effect.

Qiyām is a rukn in every prayer except nafl, in which sitting is permitted without excuse. The standing must last at least the time needed to recite one āyah, which in practice means Sūrat al-Fātiḥah plus a short sūrah; standing longer for a fuller recitation is mustaḥabb. One unable to stand, through illness, old age, or another valid ʿudhr, including inability to keep the ʿawrah covered while standing, prays seated.

Reciting at least one āyah, of whatever length, is a rukn for one capable of it. In the farḍ prayers, this rukn is discharged only in the first two rakʿāt; in Witr, sunnah and nafl it applies to every rakʿah. Correct articulation of the letters is required of one capable of it; an able reciter who fails to articulate correctly invalidates the prayer, though one with a genuine impediment (such as a stammer) is excused. The muqtadī is silent during the imam's recitation rather than reciting himself.

Rukūʿ, bowing to the extent that the hands reach the knees, the forehead roughly level with where the knees are, is a rukn in every rakʿah; prolongation is not required, the bow itself sufficing. One whose spine is naturally curved indicates the rukūʿ by bowing further still or, where that is not possible, by gesture.

Sujūd occurs twice per rakʿah, and requires that seven limbs touch the ground: both feet, both knees, both hands and the forehead; the nose is to touch alongside the forehead, and prostrating on the forehead alone without the nose, absent an excuse, is makrūh. Where an excuse (such as a wound) prevents the forehead touching, the nose alone suffices; absent an excuse, sujūd on the nose alone is not valid, and where neither can touch, sujūd is performed by gesture (īmāʾ). The surface must be firm enough to bear the weight of the forehead; where elevated, it must not exceed roughly a hand-span above the level of the feet without a valid excuse. Prostrating through a turban that has slipped down to the scalp is valid only if the forehead itself reaches the ground through it. A second sajdah begun before the worshipper has sat up, or very nearly sat up, from the first does not count as a discrete sajdah.

Al-Qaʿdah al-Akhīrah, the sitting following both sajdahs of the prayer's final rakʿah, is a rukn, its minimum duration the time needed to recite the tashahhud up to "...ʿabduhū wa rasūluh"; sitting beyond this minimum is not itself part of the rukn.

Khurūj bi-ṣunʿih, bringing the prayer to a close through an act of the worshipper's own choosing, whether the tasleem, turning the chest from the qiblah, or speech, is the seventh rukn.