Stranger in our midst

[GOTO10]

Using a while loop is the right idea. There are many ways to approach this. I personally prefer using a break to exit the loop when the stop condition is satisfied.

words = []

while True:
    new_word = input('Enter a word\n')  # str() is not needed because input() returns a string by default
    if new_word.lower() == 'stop':  # using lower() makes this comparison work for 'STOP', 'Stop', etc.
        break
    words.append(new_word)

print(words)