Alkaline and Alkali

alkaline is an adjective, describing the condition of a solution when its pH is higher than 7 .

alkali is a category of chemicals, which is sometimes defined as "soluble compound which dissolves to give hydroxide ion, and reacts with acids to give salt and water ONLY" .

examples of alkaline solutions are sodium hydroxide solution, potassium hydroxide solution, ammonia solution, calcium hydroxide solution (limewater), sodium carbonate solution, sodium hydrogencarbonate solution etc.

examples of alkalis are those highlighted in blue.
note that sodium carbonate and hydrogencarbonate are NOT alkalis.
they give alkaline solutions, but they reacts with acid to give salt, water and carbon dioxide. thus the do not fulfill the definition of "alkali" .