Minor wording changes following @juliusv review suggestions

content/docs/querying/functions.md

@@ -89,8 +89,9 @@ month for each of the given times in UTC. Returned values are from 28 to 31.
 `delta(v range-vector)` calculates the difference between the
 first and last value of each time series element in a range vector `v`,
 returning an instant vector with the given deltas and equivalent labels.
-The delta is interpolated to cover the full time range, so that it is 
-possible to get non-integer result even if the samples are all integers.
+The delta is extrapolated to cover the full time range as specified in
+the range vector selector, so that it is possible to get a non-integer
+result even if the sample values are all integers.
 
 The following example expression returns the difference in CPU temperature
 between now and 2 hours ago:
@@ -204,9 +205,10 @@ equivalent labels.
 `increase(v range-vector)` calculates the increase in the
 time series in the range vector. Breaks in monotonicity (such as counter
 resets due to target restarts) are automatically adjusted for. The
-increment is interpolated to cover the full time range, so that it is
-possible to get non-integer result even if counter increments only by
-integers.
+increase is extrapolated to cover the full time range as specified
+in the range vector selector, so that it is possible to get a
+non-integer result even if a counter increases only by integer
+increments.
 
 The following example expression returns the number of HTTP requests as measured
 over the last 5 minutes, per time series in the range vector:
@@ -215,10 +217,11 @@ over the last 5 minutes, per time series in the range vector:
 increase(http_requests_total{job="api-server"}[5m])
 ```
 
-`increase` should only be used with counters. It should be used primarily for
-human readability and is really just a syntactic sugar around `rate` times the
-number of seconds in the interval. Use `rate` in recording rules so that
-increases are tracked consistently on a per-second basis.
+`increase` should only be used with counters. It is syntactic sugar
+for `rate(v)` multiplied by the number of seconds under the specified
+time range window, and should be used primarily for human readability.
+Use `rate` in recording rules so that increases are tracked consistently
+on a per-second basis.
 
 ## `irate()`
 
@@ -306,7 +309,7 @@ regression](http://en.wikipedia.org/wiki/Simple_linear_regression).
 time series in the range vector. Breaks in monotonicity (such as counter
 resets due to target restarts) are automatically adjusted for. Also, the
 calculation extrapolates to the ends of the time range, allowing for missed
-scrapes or imperfect alignment of scrape cycle with the range's time period.
+scrapes or imperfect alignment of scrape cycles with the range's time period.
 
 The following example expression returns the per-second rate of HTTP requests as measured
 over the last 5 minutes, per time series in the range vector: