The selnolig package suppresses typographic ligatures selectively, i.e., based 
on predefined search patterns. The search patterns identify ligatures that are 
deemed inappropriate because they span morpheme boundaries. For example, the 
word *shelfful*, which is mentioned in the TeXbook as a word for which the "ff" 
ligature might be inappropriate, is automatically typeset as shelf{}ful, 
i.e., without the ff ligature.

For English and German language documents, the selnolig package provides 
extensive rules for the selective suppression of so-called "common" ligatures. 
These comprise the ff, fi, fl, ffi, and ffl ligatures as well as the ft and 
fft ligatures. Other f-ligatures, such as fb, fh, fj and fk, are suppressed 
globally. However, the package provides exceptions for names and words of 
non-English/German origin, such as fjord and Kafka.

For English language documents, the package further provides ligature 
suppression rule for a number of so-called "discretionary" or "rare" 
ligatures, such as ct, st, and sp.

The package's user guide is in the file selnolig.pdf. If you're not (yet) 
familiar with this package, you may want to at least skim the user guide in 
order to get a sense of how the package may be used.

The selnolig package requires use of the LuaLaTeX format provided by a recent 
TeX distribution, such as TeXLive2015 or MiKTeX2.9.