meaning of as adjective as structures

[majid72]

What's the meaning of as adjective as structures like " as late as" , "as early as" or as young as and etc .for example:

- The store stays open as late as midnight on sundays.(why not till midnight)
- He wakes up as early as 6 o'clock every day.(why not at six o'clock)
-Infants are listening and learning their first words as young as 10 months.
( and why not till ten months)

Thanks in advance.

[David L.]

- He wakes up as early as 6 o'clock every day.(why not at six o'clock)
If he woke up at 6 every day, then there is never a day that he sleeps in and wakes up at 7 o'clock. He would be awake, and maybe up and about at 6 a.m. Your sentence implies, when he wakes up varies from day to day, but compared to people who tend to sleep in till late, he's an early riser. Some days he will wake up earlier than others.
How early? Do you mean 7 o'clock?
Oh, earlier - as early as 6 o'clock on some mornings.

Can you see how that applies to the other sentences?

[Delmobile]

"as ... as" implies some uncertainty. If a store stays open till midnight, it's open till midnight every single day, period. But if it stays open "as late as midnight," then perhaps they close earlier, unless business is brisk, in which case they stay open...but never later than midnight.

Scientists once thought babies didn't begin to learn language until they were at least a year old, but recent research indicates that they begin to learn words as young as ten months.

[not a teacher]