diff --git a/eo-runtime/src/main/eo/org/eolang/bytes.eo b/eo-runtime/src/main/eo/org/eolang/bytes.eo
index 835d82ee57..232718fe87 100644
--- a/eo-runtime/src/main/eo/org/eolang/bytes.eo
+++ b/eo-runtime/src/main/eo/org/eolang/bytes.eo
@@ -58,9 +58,11 @@
                 * ^
 
   # Equals to another object.
+  # A condition where two objects have the same value or content.
   [b] > eq /org.eolang.bool
 
   # Total number of bytes.
+  # The complete count of bytes used to represent data.
   [] > size /org.eolang.number
 
   # Represents a sub-sequence inside the current one.
@@ -102,22 +104,22 @@
           "Can't convert non 2 length bytes to i16, bytes are %x"
           * ^
 
-  # Calculate bitwise and.
+  # Calculate the bitwise and operation.
   [b] > and /org.eolang.bytes
 
-  # Calculate bitwise or.
+  # Calculate the bitwise or operation.
   [b] > or /org.eolang.bytes
 
-  # Calculate bitwise xor.
+  # Calculate the bitwise xor operation.
   [b] > xor /org.eolang.bytes
 
-  # Calculate bitwise not.
+  # Calculate the bitwise not operation.
   [] > not /org.eolang.bytes
 
-  # Calculate bitwise left shift.
+  # Calculate the bitwise left shift.
   ^.right x.neg > [x] > left
 
-  # Calculate bitwise right shift.
+  # Calculate the bitwise right shift.
   [x] > right /org.eolang.bytes
 
   # Concatenation of two byte sequences:
diff --git a/eo-runtime/src/main/eo/org/eolang/false.eo b/eo-runtime/src/main/eo/org/eolang/false.eo
index 4edde93fbd..15dc071800 100644
--- a/eo-runtime/src/main/eo/org/eolang/false.eo
+++ b/eo-runtime/src/main/eo/org/eolang/false.eo
@@ -35,7 +35,9 @@
   right > [left right] > if
 
   # And.
+  # A logical operation that returns True only if all given conditions are true.
   ^ > [x] > and
 
   # Or.
+  # A logical operation that returns True if at least one of the given conditions is true.
   01-.eq x > [x] > or
diff --git a/eo-runtime/src/main/eo/org/eolang/fs/path.eo b/eo-runtime/src/main/eo/org/eolang/fs/path.eo
index c966c410f8..684f6eb6c7 100644
--- a/eo-runtime/src/main/eo/org/eolang/fs/path.eo
+++ b/eo-runtime/src/main/eo/org/eolang/fs/path.eo
@@ -65,6 +65,7 @@
       ^.posix.separator
 
   # POSIX specified path.
+  # A standardized way to represent file or directory locations in a Unix-like system.
   [uri] > posix
     $ > determined
     "/" > separator
diff --git a/eo-runtime/src/main/eo/org/eolang/math/angle.eo b/eo-runtime/src/main/eo/org/eolang/math/angle.eo
index 8fe1d4002d..f13168d839 100644
--- a/eo-runtime/src/main/eo/org/eolang/math/angle.eo
+++ b/eo-runtime/src/main/eo/org/eolang/math/angle.eo
@@ -29,6 +29,8 @@
 +version 0.0.0
 
 # The angle.
+# A measure of how much something is tilted or rotated, measured in degrees or radians.
+# When dataized, it shows direction or how two lines meet.
 [value] > angle
   value > @
   # Converts this from radians to degrees.
diff --git a/eo-runtime/src/main/eo/org/eolang/math/real.eo b/eo-runtime/src/main/eo/org/eolang/math/real.eo
index cfce3b224d..45505fe2be 100644
--- a/eo-runtime/src/main/eo/org/eolang/math/real.eo
+++ b/eo-runtime/src/main/eo/org/eolang/math/real.eo
@@ -35,6 +35,7 @@
   (QQ.math.real e).pow num > exp
 
   # Calculate MOD.
+  # An operation that finds the remainder after dividing one number by another.
   [x] > mod
     number ^.num.as-bytes > dividend
     number x.as-bytes > divisor
@@ -64,6 +65,7 @@
       value.neg
 
   # Make `^.num` power `x`.
+  # An operation that raises ^.num (a number) to the power of x.
   [x] > pow /org.eolang.number
 
   # Returns the positive square root of a `num`.
@@ -76,4 +78,5 @@
   [] > acos /org.eolang.number
 
   # Calculates arc sine of a `num`.
+  # An operation that finds the angle whose sine is num.
   [] > asin /org.eolang.number
diff --git a/eo-runtime/src/main/eo/org/eolang/structs/list.eo b/eo-runtime/src/main/eo/org/eolang/structs/list.eo
index 278ed5ab0b..3a37cd3b92 100644
--- a/eo-runtime/src/main/eo/org/eolang/structs/list.eo
+++ b/eo-runtime/src/main/eo/org/eolang/structs/list.eo
@@ -32,6 +32,7 @@
   origin > @
 
   # Is it empty?.
+  # A check to determine if an object contains no elements or data.
   0.eq ^.origin.length > [] > is-empty
 
   # Create a new list with this element added to the end of it.
diff --git a/eo-runtime/src/main/eo/org/eolang/true.eo b/eo-runtime/src/main/eo/org/eolang/true.eo
index 58f6741631..f220357e65 100644
--- a/eo-runtime/src/main/eo/org/eolang/true.eo
+++ b/eo-runtime/src/main/eo/org/eolang/true.eo
@@ -35,7 +35,9 @@
   left > [left right] > if
 
   # And.
+  # A logical operation that returns True only if all given conditions are true.
   01-.eq x > [x] > and
 
   # Or.
+  # A logical operation that returns True if at least one of the given conditions is true.
   ^ > [x] > or
diff --git a/eo-runtime/src/main/eo/org/eolang/txt/text.eo b/eo-runtime/src/main/eo/org/eolang/txt/text.eo
index 2f5a35041c..687336b436 100644
--- a/eo-runtime/src/main/eo/org/eolang/txt/text.eo
+++ b/eo-runtime/src/main/eo/org/eolang/txt/text.eo
@@ -32,6 +32,7 @@
 +unlint broken-ref
 
 # Text.
+# A sequence of characters representing words, sentences, or data.
 # @todo #3481:30min Remove all +unlit broken-ref from EO source code.
 #  These suppressions were added in order to be compile EO when @ref attribute
 #  from XMIR is removed, by it's checked by LintMojo. We need to remove these