First of all both terms are used to express sitting and remaining.
Usage of the terms best practice as per linguists
As for the correct Arabic usage there's a difference that may not be noticed, but
And its corresponding noun
are used to express if somebody "moved up" (from down) to sit for example from a lying position. This can already be an explanation for your inquiry as the change from a lying position to stand up often needs a short sitting...
So if you entered a room and found a person lying you'd ask them to sit saying:
The usually used example for this is the hadith of the sahabi's who mentioned the gravity false statements like here in Sahih al-Bukhari, however we may find many ahadith in which the term is used and the context is seemingly referring to usual usage of the verb
and its noun:
which refers to moving to a sitting position from a standing position (move down). Here usually
the reference examples used are verses such as (3:191) and (4:103) in which sitting is mentioned right after standing.
Duration of remaining in a sitting position
- Basically the qur'an doesn't use the verb جلس nor the term جلوس (or a sitting person جالس جليس) anywhere, but it uses the term مجلس (assembly) in its plural form once in (58:11):
O you who have believed, when you are told, "Space yourselves" in assemblies, then make space; Allah will make space for you. And when you are told, "Arise," then arise; Allah will raise those who have believed among you and those who were given knowledge, by degrees. And Allah is Acquainted with what you do.
And the verse itself shows that this sitting position is not planed for a long term usage. As it says sit and if somebody told you make space do so, meaning stand up or move and sit somewhere else for a while and so on.
- While the verb قعد and its noun قعود or قاعد or قعيد (both referring to a sitting person) have the same root as the term referring to a place of stay(and sitting for example a chair) مقعد and the term قاعدة basis, rule of tomb etc.. The later shows that the term refers to something which is intended to be lasting and not temporary as is the case with a مجلس.
Therefore the qur'an uses them when speaking of the foundations of the Ka'aba (2:127) in saying:
وَإِذْ يَرْفَعُ إِبْرَاهِيمُ الْقَوَاعِدَ مِنَ الْبَيْتِ وَإِسْمَاعِيلُ رَبَّنَا تَقَبَّلْ مِنَّا ۖ إِنَّكَ أَنتَ السَّمِيعُ الْعَلِيمُ
And [mention] when Abraham was raising the foundations of the House and [with him] Ishmael, [saying], "Our Lord, accept [this] from us. Indeed You are the Hearing, the Knowing.
Older woman who don't expect menstruation any more are also referred to as such in (24:60):
وَالْقَوَاعِدُ مِنَ النِّسَاءِ اللَّاتِي لَا يَرْجُونَ نِكَاحًا فَلَيْسَ عَلَيْهِنَّ جُنَاحٌ أَن يَضَعْنَ ثِيَابَهُنَّ غَيْرَ مُتَبَرِّجَاتٍ بِزِينَةٍ ۖ وَأَن يَسْتَعْفِفْنَ خَيْرٌ لَّهُنَّ ۗ وَاللَّهُ سَمِيعٌ عَلِيمٌ
And women of post-menstrual age who have no desire for marriage - there is no blame upon them for putting aside their outer garments [but] not displaying adornment. But to modestly refrain [from that] is better for them. And Allah is Hearing and Knowing.
One could therefore say جلس refers to a sitting which isn't intended to be long.
While قعد refers to a sitting which still could be limited, but it is at least intended with a duration of stay.
In other words both terms only become synonyms if the later has conditions for an end of the sitting and this applies for example in (3:121):
وَإِذْ غَدَوْتَ مِنْ أَهْلِكَ تُبَوِّئُ الْمُؤْمِنِينَ مَقَاعِدَ لِلْقِتَالِ ۗ وَاللَّهُ سَمِيعٌ عَلِيمٌ
And [remember] when you, [O Muhammad], left your family in the morning to post the believers at their stations for the battle [of Uhud] - and Allah is Hearing and Knowing -