1 اَسڤ3َ see 2, in two places. 2 أسّسهُ  , (S, M, Msb,) inf. n. تَأْسِيسٌ, (S, Msb, K,) He founded it; or made, or laid, a foundation, or basis, for it; (S, * Msb;) namely, a building, (S,) or a wall: (Msb:) he marked out the limits of it, (namely, of a house,) and raised its foundations: he built its foundation, or basis: (K:) he commenced it; namely, a building; as also ↓ أَسَّهُ , aor. يَؤُسُّهُ, inf. n. أَسَّ: (M:) he built it; namely, a house; (TA;) as also ↓ أَسَّهُ . (K.) You say, هٰذَا تَأْسِيسٌ حَسَنٌ [This is a good founding, or foundation]. (TA.) And مَنْ لَمْ يُؤَسِّسْ مِلْكَهُ بِالعَدْلِ هَدَمَهُ (tropical:) [He who does not lay the foundation of his property with equity, or justice, destroys it]. (A, TA.) ― -b2- أسّس زَادًا: see زَادَ in art. زود. أَسٌّ  : see what next follows, in six places. أُسٌّ  The foundation, basis, or lowest part, (S, A, Mgh, Msb, K,) of a building, (S, A, K,) or of a wall; (Mgh, Msb;) as also ↓ أَسٌّ and ↓ إِِسٌّ (A, K) and ↓ أَسَاسٌ (S, A, Mgh, Msb, K) and ↓ أَسَسٌ , (S, K,) which is a contraction of أَسَاسٌ: (S:) or the commencement of a building: and any commencement of a thing; as also ↓ أَسٌّ and ↓ أَسَاسٌ and ↓ أَسَسٌ : (M:) and the origin, source, stock, or root, (أَصْل,) of a man; as also ↓ أَسٌّ : or of anything; (M, K;) as also ↓ أَسٌّ (M, K) and ↓ إِِسٌّ and ↓ أَسِيسٌ : (K:) and the heart of a man; because [the Arabs believe that] it is the first thing that comes into existence in the womb: (M, K:) pl. آسَاسٌ (S, M, Mgh, Msb, K) and إِِسَاسٌ (M, Msb, K) and أُسُسٌ; (M, Mgh, Msb, K;) the first of which is pl. of أٌسٌّ, (Mgh, Msb,) like as أَقْفَالٌ is of قُفْلٌ; (Msb;) or of أَسَسٌ, like as أَسْبَابٌ is of سَبَبٌ; (S;) 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; (Msb;) and the third, of أَسَاسٌ, (Mgh, Msb,) like as عُنُقٌ is of عَنَاقٌ. (Msb.) You say, الأَوَّلِ ↓ بَنَى بَيْتَهُ عَلَى أَسَاسِهِ [He built his house upon its first foundation.] (A.) And قَلَعَهُ مِنْ أُسِّهِ [He uprooted it from its foundation]. (A.) And أَمْرِهِ الكَذِبُ ↓ فُلَانٌ أَسَاسُ (tropical:) [Such a one, the foundation of his affair, or case, is falsehood]. (A, TA.) And كَانَ ذٰلَكَ عَلَى أُسِّ الدَّهْرِ, (S, M, A, K,) and ↓ أَسِهِ , and ↓ إِِسِهِ , (S, M, K,) (tropical:) That was in old, or ancient, time; (S, M, K;) at the beginning of time; (S, A, * K;) and in like manner, عَلَي اسْتِ الدَّهْرِ. (A.) ― -b2- Also A remain, relic, trace, vestige, sign, mark, or track, of anything. (K.) You say, خُذْ أُسَّ الطَّرِيقِ, or الطَّرِيقِ ↓ أَسَّ , [accord. to different copies of the K, 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. (K.) أُسٌّ also signifies The remains of ashes (M, K) 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.) إِِسٌّ أس إِس اس آس آسي : see أُسٌّ, in several places. أَسَسٌ  : see أُسٌّ, in several places. أَسَاسٌ  : see أُسٌّ, in several places. أَسِيسٌ  : see أُسٌّ, in several places. Credit: Lane Lexicon