🔹 Mutter → Speaking in a low, and often annoyed way.
Example: "He muttered something under his breath when he lost the game."
(Usually implies frustration, complaining, or secrecy.)
🔹 Mumble → Speaking unclearly or indistinctly, often because of nervousness, tiredness, or shyness.
Example: "She mumbled her answer, and no one could hear her."
"What are you muttering about now?"
(Usually implies unclear pronunciation or lack of confidence.)
💡 Key point
Muttering → tone (low and often annoyed).
Mumbling → clarity (unclear or softly speech).
Complained → If someone expresses dissatisfaction openly
Grumbled → If someone mutters or speaks in a low, annoyed tone
👉 If someone is annoyed and complaining → "Grumble"
👉 If someone is speaking quietly, unclearly, or to themselves → "Mutter"