अस् (as) -- to be

पुरुष (Person) एक-वचन् (Singular) द्वि-वचन् (Dual) बहु-वचन् (Plural)
Present Tense
प्रथम् पुरुष (Third Person) अस्ति (asti) -- he is स्त: (stah) -- they (both) are सन्ति (santi) -- they (all) are
मध्यम् पुरुष (Second Person) असि (asi) -- you are स्थः (sthah) -- you (both) are स्थ​ (stha) -- you (all) are
उत्तम् पुरुष (First Person) अस्मि (asmi) -- I am स्वः (svah) -- we (both) are स्मः (smah) -- we (all) are
Imperfect Tense
प्रथम् पुरुष (Third Person) आसीत् (aaseet) -- he was आस्तां (aastaam) -- they (both) were आसन् (aasan) -- they (all) were
मध्यम् पुरुष (Second Person) आसीः (aaseeh) -- you were आस्तं (aastam) -- you (both) were आस्त​ (aasta) -- you (all) were
उत्तम् पुरुष (First Person) आसं (akaravam) -- I was आस्व (akurva) -- we (both) were आस्म​ (akurma) -- we (all) were
Future Tense
प्रथम् पुरुष (Third Person) भविष्यति (bhavishyati) -- he will be भविष्यतः (bhavishyatah) -- they (both) will be भविष्यन्ति (bhavishyanti) -- they (all) will be
मध्यम् पुरुष (Second Person) भविष्यसि (bhavishyasi) -- you will be भविष्यथः (bhavishyathah) -- you (both) will be भविष्यथ​ (bhavishyatha) -- you (all) will be
उत्तम् पुरुष (First Person) भविष्यामि (bhavishyaami) -- I will be भविष्यावः (bhavishyaavah) -- we (both) will be भविष्यामः​ (bhavishyaamah) -- we (all) will be
Imperative-mood
प्रथम् पुरुष (Third Person) अस्तु, स्तात् (astu, staat) -- let him be स्तां (staam) -- let them (both) be सन्तु (santu) -- let them (all) be
मध्यम् पुरुष (Second Person) एधि, स्तात् (edhi, staat) -- let you be स्तं (stam) -- let you (both) be स्त​ (sta) -- let you (all) be
उत्तम् पुरुष (First Person) असानि (asaani) -- let me be असाव (asaava) -- let us (both) be असाम (asaama) -- let us (all) be