What is Two capital letters printed in sequence

AB?

EF?
MN?

I am guessing from your subject title that you might refer to a line segment that has its end - points labelled as A and B

then AB is the "name" of the line segment from A to B, usually it refers to the length of that line segment

Two capital letters printed in sequence are often referred to as "letter pairs" or "letter combinations". These can be found in various contexts, such as in abbreviations, acronyms, vehicle license plates, or coding systems.

To generate a list of all possible two-letter combinations, you can use a combination of uppercase letters from the English alphabet. Assuming you want to include all 26 letters, the combinations can be found by iterating through both letters of the alphabet.

Here is a Python code snippet that generates all possible two-letter combinations:

```python
import string

letters = string.ascii_uppercase

combinations = []
for letter1 in letters:
for letter2 in letters:
combinations.append(letter1 + letter2)

print(combinations)
```

This code snippet utilizes the `string` module in Python, which provides a string containing all uppercase letters of the English alphabet. It iterates through each letter twice, combining it with every other letter. The resulting combinations are stored in a list and then printed.

Executing this code will output a list containing all 676 possible two-letter combinations.