أسّسهُ, (Ṣ, M, Mṣb,) inf. n. تَأْسِيسٌ, (Ṣ, Mṣb, Ḳ,) He founded it; or made, or laid, a foundation, or basis, for it; (Ṣ,* Mṣb;) namely, a building, (Ṣ,) or a wall: (Mṣb:) he marked out the limits of it, (namely, of a house,) and raised its foundations: he built its foundation, or basis: (Ḳ:) he commenced it; namely, a building; as alsoأَسَّهُ↓, aor. يَؤُسُّهُ, inf. n. أَسَّ: (M:) he built it; namely, a house; (TA;) as alsoأَسَّهُ↓. (Ḳ.) You say, هٰذَا تَأْسِيسٌ حَسَنٌ [This is a good founding, or foundation]. (TA.) And مَنْ لَمْ يُؤَسِّسْ مِلْكَهُ بِالعَدْلِ هَدَمَهُ ‡ [He who does not lay the foundation of his property with equity, or justice, destroys it]. (A, TA.)

أسّس زَادًا: see زَادَ in art. زود.

أُسٌّ The foundation, basis, or lowest part, (Ṣ, A, Mgh, Mṣb, Ḳ,) of a building, (Ṣ, A, Ḳ,) or of a wall; (Mgh, Mṣb;) as alsoأَسٌّ↓ andإِسٌّ↓ (A, Ḳ) andأَسَاسٌ↓ (Ṣ, A, Mgh, Mṣb, Ḳ) andأَسَسٌ↓, (Ṣ, Ḳ,) which is a contraction of أَسَاسٌ: (Ṣ:) or the commencement of a building: and any commencement of a thing; as alsoأَسٌّ↓ andأَسَاسٌ↓ andأَسَسٌ↓: (M:) and the origin, source, stock, or root, (أَصْل,) of a man; as alsoأَسٌّ↓: or of anything; (M, Ḳ;) as alsoأَسٌّ↓ (M, Ḳ) andإِسٌّ↓ andأَسِيسٌ↓: (Ḳ:) and the heart of a man; because [the Arabs believe that] it is the first thing that comes into existence in the womb: (M, Ḳ:) pl. آسَاسٌ (Ṣ, M, Mgh, Mṣb, Ḳ) and إِسَاسٌ (M, Mṣb, Ḳ) and أُسُسٌ; (M, Mgh, Mṣb, Ḳ;) the first of which is pl. of أُسٌّ, (Mgh, Mṣb,) like as أَقْفَالٌ is of قُفْلٌ; (Mṣb;) or of أَسَسٌ, like as أَسْبَابٌ is of سَبَبٌ; (Ṣ;) or, as some say, of أُسُسٌ, [like as أَعْنَاقٌ is of عُنُقٌ,] so that it is a pl. pl.; (TA;) and the second, of أَسٌّ, like as عِسَاسٌ is of عُسٌّ; (Mṣb;) and the third, of أَسَاسٌ, (Mgh, Mṣb,) like as عُنُقٌ is of عَنَاقٌ. (Mṣb.) You say,بَنَى بَيْتَهُ عَلَى أَسَاسِهِ↓ الأَوَّلِ [He built his house upon its first foundation.] (A.) And قَلَعَهُ مِنْ أُسِّهِ [He uprooted it from its foundation]. (A.) Andفُلَانٌ أَسَاسُ↓ أَمْرِهِ الكَذِبُ ‡ [Such a one, the foundation of his affair, or case, is falsehood]. (A, TA.) And كَانَ ذٰلَكَ عَلَى أُسِّ الدَّهْرِ, (Ṣ, M, A, Ḳ,) andأَسِهِ↓, andإِسِهِ↓, (Ṣ, M, Ḳ,) ‡ That was in old, or ancient, time; (Ṣ, M, Ḳ;) at the beginning of time; (Ṣ, A,* Ḳ;) and in like manner, عَلَى ٱسْتِ الدَّهْرِ. (A.)

Also A remain, relic, trace, vestige, sign, mark, or track, of anything. (Ḳ.) You say, خُذْ أُسَّ الطَّرِيقِ, orأَسَّ↓ الطَّرِيقِ, [accord. to different copies of the Ḳ, meaning, Take thou to the track of the way,] when one guides himself by any mark or track, or by camels' dung: but when the way is manifest, you say, خُذْ شَرَكَ الطَّرِيقِ. (Ḳ.) أُسٌّ also signifies The remains of ashes (M, Ḳ) between the أَثَافِى, q.v.: (M:) occurring in a verse of En-Nábighah Edh-Dhubyánee; but accord. to most relates of this verse, it is آسٌ. (TA.)