noun
seam allowance; margin for a seam
The extra fabric beyond the stitching line, used in sewing to join pieces and finish edges.
型紙には縫い代を含めてください。
Please include the seam allowance in the pattern.
縫い代を1センチ取って裁断する。
Cut the fabric with a 1 cm seam allowance.
Variant without okurigana; less common but still seen.
縫い目 refers to the seam line or stitches themselves, while 縫い代 is the extra fabric allowance beyond the stitching.
Compound of 縫い (nui, 'sewing', the continuative form of 縫う) and 代 (shiro, 'allowance, margin').