什么是（内部或外部的）内错角？

Before identifying what consecutive interior and consecutive exterior angles are, we will first break down the term word by word.

When angles are consecutive, they lie on the same side of the transversal. Consider the word 'consecutive'. Consecutive means to follow continuously. The angles follow each other on the same side of the line consecutively.

In the figure above, the transversal separates the figure into its consecutive sides.

$\angle{A}, \angle{B}, \angle{C}, \angle{D}$ are all consecutive angles because they lie on the same side of the transversal.

Similarly, $\angle{E}, \angle{F}, \angle{G}, \angle{H}$ are all consecutive angles because they lie on the same side of the transversal.

Next, let's consider the difference between interior and exterior angles.

In contrast to consecutive angles that deal with the transversal, interior and exterior angles deal with the two lines that are not the transversal.

Consider the same figure below.

In the figure above, the two parallel lines create interior and exterior angles.

The top and bottom regions (green) represent the exterior angles, while the region inside (purple) shows the interior angles.

Now let's put the two terms together!

Let's start with consecutive interior angles.

We know that consecutive angles are positioned on the same side of the transversal. We also know that the angles inside the two parallel lines are interior angles.

To identify consecutive interior angles, we simply find the angles that lie on the same side of the transversal and lie inside the two parallel lines.

In the figure above, $\angle{4}$ and $\angle{6}$ (pink) are consecutive interior angles. Additionally, $\angle{3}$ and $\angle{5}$ (blue) are consecutive interior angles.

Both pairs of angles lie on the same side of the transversal.

Now let's consider consecutive exterior angles.

We know that consecutive angles are positioned on the same side of the transversal. We also know that the angles outside the two parallel lines are exterior angles.

To identify consecutive exterior angles, we simply find the angles that lie on same side of the transversal and lie outside the two parallel lines.

In the figure above, $\angle{2}$ and $\angle{8}$ (purple) are consecutive exterior angles. We also see that $\angle{1}$ and $\angle{7}$ (green) are consecutive exterior angles.

To sum it all up:

Consecutive exterior angles are supplementary and consecutive interior angles are supplementary.

Consecutive exterior angles are two exterior angles on the same side of a transversal.

Consecutive interior angles are two interior angles which lie on the same side of the transversal.

Consecutive interior angles:

Consecutive interior angles are interior angles that lie on the same side of the transversal. Take a look at the following picture:

As you can see, $\angle B$ and $\angle C$ are circled in blue, and $\angle G$ and $\angle F$ are circled in red. All of these are the interior angles: they are located in between the two vertical lines.

Notice that $\angle B$ and $\angle C$ are on the same side of the transversal $-$ you don't have to go across the transversal to get from one angle to the other. Since they are also interior angles, $\angle B$ and $\angle C$ are consecutive interior angles.

Likewise, since $\angle G$ and $\angle F$ are interior angles that are on the same side of the transversal, they are also consecutive interior angles.

Let's practice identifying consecutive interior angles!

Angles $3, 4, 5,$ and $6$ are interior angles because they are in between Line A and Line B. Notice that Lines A and B don't have to be parallel to find the interior angles!

Next question:

Angle $5$ and Angle $2$ are consecutive interior angles because they are interior angles that lie on the same side of the transversal. Angle $3$ and Angle $8$ are also consecutive interior angles for the same reason.

Consecutive exterior angles:

Consecutive exterior angles are exterior angles that lie on the same side of the transversal. Take a look at the following picture:

As you can see, $\angle A$ and $\angle D$ are circled in green, and $\angle H$ and $\angle E$ are circled in orange. All of these are the exterior angles: they are located on the outsides of the two vertical lines $-$ not in between the vertical lines.

Notice that $\angle A$ and $\angle D$ are on the same side of the transversal $-$ you don't have to go across the transversal to get from one angle to the other. Since they are also exterior angles, $\angle A$ and $\angle D$ are consecutive exterior angles.

Likewise, since $\angle H$ and $\angle E$ are exterior angles that are on the same side of the transversal, they are also consecutive exterior angles.

Let's practice identifying consecutive exterior angles!

Angles $1, 2, 7,$ and $8$ are exterior angles because they are located on the outsides of Line A and Line B $-$ not between these lines. Notice that Lines A and B don't have to be parallel to find the exterior angles!

Next question:

Angle $1$ and Angle $6$ are consecutive exterior angles because they are exterior angles that lie on the same side of the transversal. Angle $7$ and Angle $4$ are also consecutive exterior angles for the same reason.