الأحد
كلمة (الأحد) في اللغة لها معنيانِ؛ أحدهما: أولُ العَدَد،...
Calmness and steadiness of all parts of the body for an interval of time in all the physical pillars of prayer.
"Tuma’neenah" (tranquility) means allowing the parts of the body to settle and stop their movement for a period of time, the least of which is the time it takes to make the obligatory "dhikr" for that particular position in prayer, for example, the time to say: "Subhāna Rabbi-al-‘Azheem" [Glory be to Allah, my Lord, the Greatest].
"Tuma’neenah": calmness and serenity. Opposite: "idtirāb" (confusion) and "qalaq" (anxiety). Original meaning: settling, stability, and steadiness. Other meanings: finding intimacy and comfort (in the company of someone or something), comfort, confidence, security.
That one feels relaxed, still, stable and has no worry or agitation, and is calm and steady after having gone through a state of uneasiness.