Function of a dagesh

Question

Occasionally Hebrew letters in Tanach have a dagesh mark. I saw one in a khaf sofit, as at the end of the second line of the Priestly Blessing and the 4th line of Ashrei, and it sparked my interest. What function does that dagesh serve?

I do not understand the function of a dagesh in general. If the dagesh in a khaf sofit has a function no different from any other dagesh, please tell me about that general function. I would like to know why a dagesh appears relatively rarely in a khaf sofit and what it's function is when it appears.

The wiki article https://en.wikipedia.org/wiki/Dagesh does not explain why the dagesh is sometimes found in a khaf sofit and more often not.

Answer 1

A dot in a Hebrew letter indicates a strengthening of the sound of the letter.

For letters that have two ways of reading them, the dot indicates it's the 'harder' version that is to be used here.

In the letters בגדכפת the mark doing that is called a "dagesh kal" or "dagesh lene" or "weak dagesh" and it means to use the plosive version of the letters instead of the fricative form.

In the letters אהוי the mark doing that is called a "mappik" and it means the letter is a consonant not a mater lectionis. (Note a mappik is often omitted from writing when the status of the letter is obvious from context, such as where the letter is already marked with its own vowel.)

Otherwise (and sometimes in addition to the above function), a dot indicates the consonant is to be germinated. This version is called a "dagesh chazak" or "dagesh forte" or "strong dagesh".

A line on top of a letter (rafe) indicates the opposite: the weaker (or non-geminated) form is to be used.

Which form of a letter to use where depends on the conjugation and construction of the given word. Some letters are bound to have certain forms more or less often depending on how often they are used in prefixes, suffixes, and in different places in a root. There's no way to give a fixed rule for how often one form should show up.