Abarim Publications' online Biblical Hebrew Dictionary
According to BDB Theological Dictionary there's no real Hebrew root ספר (spr) because all words of this form are (probably) derived from an Assyrian loanword saparu, meaning to send (a message). HAW Theological Wordbook of the Old Testament reports it comes from Akkadian words meaning writing or scribe, and that the root even means "to set out on a journey" in some Semitic regions. But wherever it came from, these loanwords paid off in quite a few derived Biblical words (and names):
It needs to be noted that the development of the art of recording is a major theme in the Bible, and writing may have seemed magic or telepathic to early audiences, but in fact it should be classed as information technology. The invention of effective recording technology (most notably the Semitic alphabet) allowed data to be easily preserved, transported and transmitted. Prior to this, writing and record-handling was governed by privileged priestly classes but when the alphabet was devised, all common people could be priests and thus handle information. This is what gave the Semites their celebrated advantage over Egypt (hence the Exodus) and hence the Lord's invitation to Israel to become to Him a kingdom of priests (Exodus 19:6).
- The masculine noun ספר (seper), denoting various kinds of writings: historical records (Genesis 5:1), legal documents (Deuteronomy 24:1), legal codes (Exodus 24:7), prophetic messages (Jeremiah 25:13).
- The feminine noun ספרה (sipra), also meaning book. This feminine variant occurs only once, in Psalm 56:8.
- The denominative verb ספר (sapar), which would be expected to mean to write or produce a ספר (seper), but is actually used only of general mathematical activity (in the words of HAW Theological Wordbook of the Old Testament): to count things (Genesis 15:5), to carefully observe (Job 14:16) or to recount (Judges 6:13).
- The masculine noun ספר (sopor) or ספור (sopor), meaning scribe, or someone who produces a ספר (seper) (Judges 5:14, Jeremiah 36:26).
- The masculine noun ספר (separ), meaning census (2 Chronicles 2:16 only).
- The feminine noun ספרה (sepora), meaning number, sum or amount (Psalm 71:15 only).
- The masculine noun מספר (mispar), meaning number or recount (Deuteronomy 33:6, Judges 7:14). Since innumerability goes hand in hand with a very large amount, our word מספר (mispar) is sometimes used to refer to a relatively small amount; one that's easily counted (Numbers 9:20, Deuteronomy 33:6). In the same vein, coupled with the particle of negation אין ('ayin), which expresses an absence, the term אין מספר, meaning 'without number' is formed (Job 21:33, Psalm 40:12).