Is samadhi the same as samatha? Is there khanika samatha? I read the following on the internet:

Notice there's a wide spectrum on the Samatha/Vipassana scale, but
even on the extreme spectrum of Vipassana, the &quot;dry-insight&quot;, there's
still element of Samatha ( the khanika/Samadhi/Momentary Concentration,
see Ven. Gunaratana's &quot;The Jhanas&quot; for more details ).

It is said the Buddhist commentaries refer to Khanika (momentary), Upacara (neighborhood) and Appana (attainment) Samadhi.
Are 'samatha' &amp; 'samadhi' synonymous?  Does Buddhism refer to Khanika/Momentary Samatha?
If I sit dow on the cushion for a moment, that's momentary samatha. Samatha is simply calmimg.  It can take place anywhere.  Samatha can lead to samadhi, but the two are by no means identical.  It would be akin to equating the ingredients to a fully baked cake.