These are so-called minimal pairs, which means that they differ in one sound only: thread [θred] vs. threat [θret] If differentiating [d] from [t] seems a bit complicated, when you hear these words in a meaningful context (e.g. in sentences/conversations), then it will be easier.

They sound very similar but they ARE different. I pronounce the "d" pronounced slightly further back in my mouth, not touching my teeth. The final "t" in threat I pronounce with my tongue actually hitting my teeth and with slightly more breath. I think the vowel/dipthong is also very slightly longer on thread. Maybe a language teacher can give you the correct explanation.

As nouns the difference between thread and threat is that thread is a long, thin and flexible form of material, generally with a round cross-section, used in sewing, weaving or in the construction of string while threat is an expression of intent to injure or punish another. As verbs the difference between thread and threat is that thread is to put thread through while threat is (label) to press; urge; compel.

The vowel sound, shown by the letters "ea," is "singable." You can hum it. Your vocal chords or going. In both words, in the final "d" or "t" your lips move exactly the same way. In "threat," you stop "singing" the vowel before you get to the final "t." The "t" is just a puff of air. In "thread," you keep singing while you close off the word with the d. In real life, we tell the difference mostly from context, because the meaning of the two words is completely different. Which is more likely? "The parent made a threat. 'If you don't do your homework, I won't let you go out with your friends." "The parent made a thread. 'If you don't do your homework, I won't let you go out with your friends." "Make a thread" doesn't make sense (unless you are a spider!) Which is more likely? "In order to sew the patch on your shirt, I need a spool of black threat." "In order to sew the patch on your shirt, I need a spool of black thread." https://voca.ro/1xN2Y1tf52Rl