Concrete Shape Terminology

Fy	The yield stress of the reinforcing bars.
f'c	The 28-day concrete compressive strength.
f"c	The maximum concrete compressive stress.
eu	The ultimate concrete strain.
eo	The concrete strain at the maximum compressive stress.
e	Extreme compression fiber strain under the loading specified.
Maximum Stress Factor, k	Multiplier for the compressive strength, f'c, to obtain the maximum compressive stress, f"c.
Confinement Factor, g	The confinement factor used to calculate the compressive stress at the ultimate concrete strain.

Uncracked Concrete Transformed Section Properties

Modular Ratio, n	The ratio of the modulus of elasticity of steel (Es) to the modulus of elasticity of concrete (Ec).
Area	Area of the cross section.
Xc, Yc	X and Y coordinates of the cross-section's centroid relative to the global origin.
Ix, Iy	Moment of inertia about the centroidal x and y-axes
Ixy	Product of inertia about the centroidal x and y-axes
Sx+, Sx-, Sy+, Sy-	Elastic section modulus about the centroidal axis (x or y) with respect to the extreme fiber in the positive or negative direction.
fcr	The Modulus of Rupture
Mcr Top Mcr Bottom Mcr Right Mcr Left	The cracking moment for bending about the x and y axes. The Mcr Right corresponds to the right side of the section being in tension, etc.
Note: Applicable properties are transformed to concrete.

Cracked Concrete Section Properties

N.A. Offset	Perpendicular distance from the neutral axis to the centroid under the loading specified.
N.A. Angle	Neutral axis inclination angle measure ccw from the X-axis under the loading specified.
Icr X, Icr Y	Moments of inertia of the cracked section about the X and Y-axes.

Interaction Surface Points

Po, To	The axial only capacity of the section. Calculated based on a load that causes crushing of the concrete (compression) and/or yielding of the reinforcement (tension, compression).
Mox, Moy	The uniaxial moment capacity of the section for bending about the x and y-axes.
Pbx, Pby, Mbx, Mby	The balance points (i.e. transition points) on the Interaction Diagram for Axial-Moment interaction caused by bending about the x and y-axes.
Note: These extreme points on the Interaction Diagrams are modified by the Strength Reduction Factors (f) when specified