How do we know when to use these sounds?

Unfortunately, there is not a perfect set of rules to always know which TH sound to use.

There are many exceptions, but here are some general guidelines…

The Unvoiced TH sound is used most often for content words.

Content words are words that have more meaning. They are often thought of as the more “important” words in a sentence. This TH sound usually appears at the beginning or end, but sometimes appears in the middle of a word. If it appears in the middle, the way you can know it should be pronounced with an unvoiced TH sound is if it is followed by a consonant.

Examples:

Beginning: Thankful, throw

End: bath, strength

Sometimes middle (if followed by consonant): bathtub

***But please note that sometimes unvoiced TH sounds appear in the middle of the word even when vowels come before and after.

The Voiced TH sound is used mostly for “structure” words in English…

These words typically don’t have much meaning by themselves, but are important for the structure/grammar of a sentence.

Often, these words are shorter. This allows us to say them quicker and our tongues don’t have to work as hard to come all the way beyond the teeth.

Examples: This, that, these, those, the, there, then, though

Think about how often we use these words in a sentence.

Even though the TH Voiced sound is not a classic sound, it is still very common because of the type of words we use it for.

So even though the Voiced TH Sound list has far fewer words, you still need to be able to make this sound correctly to sound like a native speaker.

As we mentioned, when TH appears in the middle followed by a consonant, it is usually unvoiced. As in, bathtub.

But, TH in the middle of words with vowels coming before and after usually means voiced as in, brother or weather.