My students come up with such good questions about English! I thought this was an excellent one to share with you all: Why does exactly sound like egg-zakly?
The letter X is pronounced "KS." So the original word was pronounced ek-sakt-ly. But over time the pronunciation changed and the sounds blended together.
K and S are voiceless sounds, which means that they do not use the voice from the vocal cords in the throat. Instead they are just pronounced with air. They are quiet sounds. However, the E at the beginning of the word and the A after the X, are voiced sounds. They are loud sounds, pronounced with vibration from the vocal cords. Over generations, people took the voicing of the E and A and continued it into the K and S sounds. When K is pronounced with voice it becomes a G, and when S is voiced, it becomes a Z. These pairs of sounds, K/G and S/Z, are pronounced exactly the same in the mouth, except for the voicing.
So nowadays we voice the whole beginning of the word: eg-za instead of ek-sa. This is a pronunciation process called assimilation, and it can happen when sounds are close together in a word. Quite a few words that have the same beginning sound (ex) are pronounced this way:
If the X is followed by a T (or another voiceless sound), it generally won't become voiced, because the T is voiceless and keeps the KS from voicing.
extent--ekstent (T is voiceless)
express--ekspress (P is voiceless)
There are quite a few assimilation rules in English, so it's a good thing to know about!
Okay, what about the missing T? Pronouncing the consonant cluster /ktl/ from exactly isn't very easy. To do it correctly you have to say it very slowly. But native speakers like to speak quickly! It is much faster to pronounce it by leaving out the T. So in both American and British English it is pronounced without the T:
So now you know! When you pronounce exactly remember the "egg." Hope this helps! Keep on learning English!