Do you know the DIFFERENCE?

坂   and   阪

Both mean HILL or SLOPE and both have the same readings.

Meaning: slope; incline; hill
Kun: さか
On: ハン

However, only this one is used for a literal "hill" today:

KANJI PARTS:

• 土 (dirt) 
• 反 (return; go back)

To return 反 to dirt 土 may imply death. While 坂 today doesn't have that connotation (it just means "hill"), that might explain why...

This one is only used in names such as 大阪 Osaka

KANJI PARTS:

• 阝 (mound; dam) 
• 反 (return; go back)

While it is used with people's names like 阪本 sakamoto, this character alone usually represents 大阪 Osaka.

Here are a few Osaka-related words:

• 大阪府(おおさかふ) Osaka prefecture
• 阪神(はんしん) Osaka-Kobe
• 京阪(けいはん) Kyoto-Osaka
• 在阪(ざいはん) being in Osaka
• 帰阪(きはん) returning to Osaka

And, finally, a proverb:

口(くち)では大阪(おおさか)の城(しろ)も建(た)つ。

To build Osaka castle by talking.

(talk is cheap; easier said than done)