An absorbent article comprising: a cover layer; a barrier layer; an absorbent system arranged between said cover layer and said barrier layer; wherein said absorbent article has a thickness of less than 2.5 mm; and wherein at least a portion of said absorbent article satisfies one of the two following equations: AI > 2.37 − 0.77 ln BW / MCB , where BW/MCB is ≤ 5.9; and AI > 1.0 , where BW/MCB is > 5.9. wherein MCB = Modified Circular Bend Stiffness; BW = Basis Weight of the Article; and AI = Absorbency Index, wherein AI = 6.27 − R 6.12 + 499 − FPT 495 ; wherein R = Rewet Value; and FPT = Fluid Penetration Time; and wherein the Modified Circular Bend Stiffness (MCB), the Basis Weight (BW), the Rewet Value (R), and the Fluid Penetration Time (FPT) are measured using the methods described in the description; wherein (i) when AI > 1.0, where BW/MCB is > 5.9 said absorbent system is substantially entirely SAP, wherein said SAP has an absorbent capacity of at least 20 g/g after 1 minute, and a total capacity of at least 40 g/g; wherein said SAP is secured by adhesive; and wherein said SAP has a gel blocking ratio of at least 0.50; and (ii) when AI > 2.37 - 0.77 ln(BW/MCB), where BW/MCB is ≤ 5.9, said absorbent system includes a material containing a mixture of from 90% to 40% cellulosic fibers and 10% to 60% of superabsorbent polymer (SAP). a cover layer; a barrier layer; an absorbent system arranged between said cover layer and said barrier layer; wherein said absorbent article has a thickness of less than 2.5 mm; and wherein at least a portion of said absorbent article satisfies one of the two following equations: AI > 2.37 − 0.77 ln BW / MCB , where BW/MCB is ≤ 5.9; and AI > 1.0 , where BW/MCB is > 5.9. wherein MCB = Modified Circular Bend Stiffness; BW = Basis Weight of the Article; and AI = Absorbency Index, wherein AI = 6.27 − R 6.12 + 499 − FPT 495 ; wherein R = Rewet Value; and FPT = Fluid Penetration Time; and wherein MCB = Modified Circular Bend Stiffness; BW = Basis Weight of the Article; and AI = Absorbency Index, wherein AI = 6.27 − R 6.12 + 499 − FPT 495 ; wherein R = Rewet Value; and FPT = Fluid Penetration Time; and wherein the Modified Circular Bend Stiffness (MCB), the Basis Weight (BW), the Rewet Value (R), and the Fluid Penetration Time (FPT) are measured using the methods described in the description; wherein (i) when AI > 1.0, where BW/MCB is > 5.9 said absorbent system is substantially entirely SAP, wherein said SAP has an absorbent capacity of at least 20 g/g after 1 minute, and a total capacity of at least 40 g/g; wherein said SAP is secured by adhesive; and wherein said SAP has a gel blocking ratio of at least 0.50; and (ii) when AI > 2.37 - 0.77 ln(BW/MCB), where BW/MCB is ≤ 5.9, said absorbent system includes a material containing a mixture of from 90% to 40% cellulosic fibers and 10% to 60% of superabsorbent polymer (SAP). (i) when AI > 1.0, where BW/MCB is > 5.9 said absorbent system is substantially entirely SAP, wherein said SAP has an absorbent capacity of at least 20 g/g after 1 minute, and a total capacity of at least 40 g/g; wherein said SAP is secured by adhesive; and wherein said SAP has a gel blocking ratio of at least 0.50; and (ii) when AI > 2.37 - 0.77 ln(BW/MCB), where BW/MCB is ≤ 5.9, said absorbent system includes a material containing a mixture of from 90% to 40% cellulosic fibers and 10% to 60% of superabsorbent polymer (SAP). <EOS>