Below definitions are in ASTM A480-17 (for reference)
Plate, n—material 3 ⁄ 16 in. [5.00 mm] and over in thickness and over 10 in. [250 mm] in width. Finishes for plate are actually shown in Section 13 of ASTM A480.
Sheet, n—material under 3 ⁄ 16 in. [5.00 mm] in thickness and 24 in. [600 mm] and over in width. Finishes for sheet are actually shown in Section 11 of ASTM A480.
Strip, n—cold-rolled material under 3 ⁄ 16 in. [5.00 mm] in thickness and under 24 in. [600 mm] in width. Finishes are detailed in Section 12 for strip, and strip edges in Section 14 for Cold-Rolled Strip of ASTM A480.