dts are called tooth sounds,

because when you pronounce d-, t-, s-,

your tongue will touch your teeth, or almost touch.

They are interchangeable to make words.

As we just mentioned, from potion

to poison, t- to s-.

Take a look at three examples.

Send, sent: from d- to t- to make past tense.

spend, spent: from d- to t- to make past tense.

wise, wit: from adjective to noun,

from s- to t-.

So, don't forget dts are interchangeable.

We all know a sample word, 'sit.'

From sit come the words seat, saddle, settee, and sedan.

You may sit on any one of them.

Now you may see that i- in sit changes into ea- in seat,

a- in saddle, e- in settee and sedan.

And t- in sit becomes d- in saddle and sedan.

So, I use two rules: aeiou and dts, interchangeable.

Usually people sit in a meeting,

instead of standing, so a meeting is

also called a session.

As you can see, 'sess' is a word root, which means sit.

i- in sit becomes e- in sess-.

The t- in sit becomes s-.

dts, they are interchangeable.

aeiou, they are interchangeable.

Let's take one step further.

A word root from Greek 'cid-', meaning falling down, also comes from 'sit.'

Perhaps when you sit down, your body will falls down at the same time.

As you can see, if c- pronounces s-,

then, it is interchangeable with s-.

i- to i-.

d- in cid is t- in sit.

Occident means the west, where the sun falls down.

oc- in occident comes from ob-.

It means down.

And cid- means falling down.

So it emphasizes 'fall down.'

This is the place where the sun falls down.

This is the place the sun sets, the west.

An accident is something that falls down unexpectedly,

and give us a great surprise.

In other words, we don't know such a thing will happen.

It is an accident.

An incident is something that falls down within our expectation.

'in-' here means within.

Fall within our expectation.

We know such a thing may happen and it did happen.

One of my favorite movies is 'Sinjuki Incident.'

The police know such a thing will happen.

And it did.

From feet, we gain two word roots, ped- and pet-.

F- in feet becomes p-.

bpfv, they are interchangeable.

And ee- becomes one e-.

And t- becomes d- or t-.

Therefore, you can see

ped- and pet-, they are from feet.

Both roots share the meaning of feet and walking.

But you got to pay attention to this.

pet- has a more specific purpose.

It has a very specific goal.

For example, a pedal is something you put your foot on.

A bicycle pedal, for example.

And expedition means walking out.

'ex-' here means 'out'.

Whenever you see an ex- in the front of a word,

you know it means 'out,' 'go out, walk out.'

In a game, many players compete together for a prize.

Com- is short for 'come' which means 'together'.

When you try to gather people, you will say, 'Come! Come! Come!'

'Everybody come!'

Therefore, compete means 'play together for a very specific goal.

And a competent person is able to win in a game.

-Ent is the word end for adjective.