sleeve and jacket

These are notes on the sleeve and the jacket:
the sleeve is a pattern piece and the area around the armhole is a pattern piece and the sleeve must be fitted into the armhole. This is the right word: 'to fit'.

When sewing the sleeve in, the sleeve is sewn right side to right side. Use a gathering stitch to ease the sleeve piece in ; There is also the matching of the points on the sleeve to the armhole-
The sleeve seam is sewn as well as the underarm side seam and shoulder seam; thus the sleeve is inserted into the circular hole-
The nature of sewing-in, fitting-in must be exact and precise- seam allowances should be commensurate with the aim of fitting the sleeve in - In suits and jackets you note a certain puffiness at the sleeve area- sometimes there is a tightness--
How do we get the right degree of puffiness?; How do we 'ease' this tightness away for better comfort while also maintaining that degree of formality ; Formality and informality are important elements of the jacket.