Select the most appropriate one-word substitution for the given group of words.

A speech expressing one’s thoughts aloud to oneself

soliloquy

The most appropriate one-word substitution for "a speech expressing one's thoughts aloud to oneself" is soliloquy.

The other words in the options, harangue, hyperbole, and sacrilege, do not mean the same thing.

• Harangue is a long, forceful speech, especially one that is critical or aggressive.
• Hyperbole is an exaggeration or overstatement.
• Sacrilege is an act of disrespect or irreverence towards something sacred.

A soliloquy is a speech that a character in a play or film delivers to themselves, without any other characters present. It is a way for the character to express their thoughts and feelings without having to worry about how others will react.