The "th" sound and the "s" sound at the end of a word are produced differently and have distinct phonetic characteristics.
The "th" sound, also known as the voiceless dental fricative, is produced by placing the tip of the tongue between the teeth and blowing air gently between them. It is found in words like "bath," "teeth," or "both." When producing the "th" sound, the vocal cords are not involved, resulting in a soft, breathy sound.
On the other hand, the "s" sound, known as the voiceless alveolar fricative, is produced by raising the front part of the tongue to the alveolar ridge, the area just behind the upper front teeth, and releasing a stream of air over the sides of the tongue. It is found in words like "cats," "kiss," or "buses." Unlike the "th" sound, the "s" sound involves the vocal cords, resulting in a hissing sound.
In terms of pronunciation, the "th" sound is typically softer and more gentle compared to the "s" sound, which has a sharper and more pronounced hissing quality. The "th" sound is also less common in many languages compared to the "s" sound.
It's worth noting that the exact pronunciation of these sounds can vary depending on regional accents and individual speech patterns.