A polymer comprising m repeating units, wherein an n th repeating unit of the m repeating units is a first repeating unit represented by Formula 1 below, wherein, when estimated by density functional theory using the B3LYP exchange functional and a 6-31+G(d) basis set, at least one of a first dihedral angle between an A 1 ring of the n th repeating unit and a first aromatic ring of an (n-1) th repeating unit and a second dihedral angle between an A 2 ring of the n th repeating unit and a second aromatic ring of a (n+1) th repeating unit is equal to or greater than an angle of χ 50% represented by Equation 1: χ 50 ⁢ % = A + B φ + 4 θ wherein the first aromatic ring is bound to the A 1 ring by a single bond; the second aromatic ring is bound to the A 2 ring by a single bond; R 1 to R 7 of Formula 1 are each independently one of a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 3 -C 60 cycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 2 -C 60 heteroaryl group, -N(Q 1)(Q 2), and -Si(Q 3)(Q 4)(Q 5), wherein Q 1 to Q 5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 3 -C 60 cycloalkyl group, a C 6 -C 60 aryl group, or a C 2 -C 60 heteroaryl group; X of Formula 1 is a single bond, or a linker including carbon or a Group 16 element; m is an integer from 2 to 1000; n is a variable of from 2 to m-1; A of Formula 1 is 26.03, and B is 0.0445; φ of Equation 1 is an angle between the A 1 ring and A 2 ring of Formula 1, as illustrated in Formula 1-1 below; and θ of Equation 1 is an angle between a first imaginary line extending from a bond between the A 1 ring and a A 3 ring of Formula 1 in a direction close to nitrogen of the A 3 ring and a second imaginary line extending from a bond between the A 2 ring and A 3 ring in a direction close to the nitrogen of the A 3 ring, as illustrated in Formula 1-2 below: wherein the polymer further comprises a second repeating unit represented by Formula 5A, 5B, 5C, 5D, or 5E below: wherein, in Formulae 5A to 5E, R 21 and R 22 are each independently a substituted or unsubstituted C 1 -C 60 alkyl group; and Y 1 to Y 4 are each independently a hydrogen atom, a substituted or unsubstituted C 1 -C 60 alkyl group, or a substituted or unsubstituted C 1 -C 60 alkoxy group, or a combination thereof. wherein the first aromatic ring is bound to the A 1 ring by a single bond; the second aromatic ring is bound to the A 2 ring by a single bond; R 1 to R 7 of Formula 1 are each independently one of a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a substituted or unsubstituted C 1 -C 60 alkyl group, a substituted or unsubstituted C 2 -C 60 alkenyl group, a substituted or unsubstituted C 2 -C 60 alkynyl group, a substituted or unsubstituted C 1 -C 60 alkoxy group, a substituted or unsubstituted C 3 -C 60 cycloalkyl group, a substituted or unsubstituted C 3 -C 60 cycloalkenyl group, a substituted or unsubstituted C 6 -C 60 aryl group, a substituted or unsubstituted C 6 -C 60 aryloxy group, a substituted or unsubstituted C 6 -C 60 arylthio group, a substituted or unsubstituted C 2 -C 60 heteroaryl group, -N(Q 1)(Q 2), and -Si(Q 3)(Q 4)(Q 5), wherein Q 1 to Q 5 are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, a C 1 -C 60 alkyl group, a C 2 -C 60 alkenyl group, a C 2 -C 60 alkynyl group, a C 3 -C 60 cycloalkyl group, a C 6 -C 60 aryl group, or a C 2 -C 60 heteroaryl group; X of Formula 1 is a single bond, or a linker including carbon or a Group 16 element; m is an integer from 2 to 1000; n is a variable of from 2 to m-1; A of Formula 1 is 26.03, and B is 0.0445; φ of Equation 1 is an angle between the A 1 ring and A 2 ring of Formula 1, as illustrated in Formula 1-1 below; and θ of Equation 1 is an angle between a first imaginary line extending from a bond between the A 1 ring and a A 3 ring of Formula 1 in a direction close to nitrogen of the A 3 ring and a second imaginary line extending from a bond between the A 2 ring and A 3 ring in a direction close to the nitrogen of the A 3 ring, as illustrated in Formula 1-2 below: φ of Equation 1 is an angle between the A 1 ring and A 2 ring of Formula 1, as illustrated in Formula 1-1 below; and θ of Equation 1 is an angle between a first imaginary line extending from a bond between the A 1 ring and a A 3 ring of Formula 1 in a direction close to nitrogen of the A 3 ring and a second imaginary line extending from a bond between the A 2 ring and A 3 ring in a direction close to the nitrogen of the A 3 ring, as illustrated in Formula 1-2 below: wherein, in Formulae 5A to 5E, R 21 and R 22 are each independently a substituted or unsubstituted C 1 -C 60 alkyl group; and Y 1 to Y 4 are each independently a hydrogen atom, a substituted or unsubstituted C 1 -C 60 alkyl group, or a substituted or unsubstituted C 1 -C 60 alkoxy group, or a combination thereof.