Both ῤῆμα and λόγος are translated ‘word' and ‘words.' ῤήμα is the saying, the thing spoken (έρῶ, εἴρηκα, 'to speak'); it is more individual than λόγος, standing in relation to it rather as a part to the whole. λόγος includes the thoughts as well as the utterance. Compare the use of the French mot with parole.
The words have been thus distinguished: λόγος is the deeper, fuller word; it is the revelation of what is in God, in His nature and character ― His love, His ways ― in short, all that He communicates: ῤῆμα is the actual communication. λόγος (from λέγω, 'to speak') is that which is known in the mind, and known by expressing it. I cannot think without having a thought, and λόγος is used for that, and the expression of it: it is the matter and form of thought and expression, as well as the expression of it. It is a word so large in sense as to be very hard to express. ῤῆμα is the actual utterance.
If this distinction be borne in mind, the following passages will be the better apprehended. For λόγος, Matt. 13:19; Mark 14:39, ‘word' not ‘words' (compared with Matt. 26:44); Mark 7:13; 16:20; Luke 1:2; Acts 4:31; 6:4; Rom. 9:6; Heb. 4:12; 6:1; Jas. 1:18; 1 Pet. 1:23. And it will be understood how characteristic λόγος is of John's writings: chap. 1:1, 14; 5:24, 38; 8:31, 37, 43; and in verses 51, 52, and 55 (where it is the same ― 'word,' instead of ‘saying' as in the A. V.); 10:35; 14:23, 24 (‘word' and ‘words,' not ‘words' and ‘sayings' as the A. V.); 15:3, 20; 17:6, 14, 17; 1 John 1:1.
Yet the apostle also uses ῤῆμα: John 3:34; 6:63, 68; 8:47; 12:47, 48; 14:10; 17:8. Compare also Matt. 4:4; Eph. 6:17 (not the book merely, but the text); Matt. 26:75; Luke 5:5; Rom. 10:8, 17; Heb. 1:3; 6:5; 11:3; 1 Pet. 1:25. These will suffice to illustrate the use of the word, which has the force more of individual utterances, divine communications.
λαλιά (from λαλέω, ‘to talk, utter a sound') is, as a substantive, of much more limited use, as it is of meaning, being in fact only found in Matt. 26:73 = Mark 14:70; John 4:42 (comp. λόγος, verse 41); and 8:43. But the constant use of the verb for the fact of uttering human language (Matt. 9:33; Mark 16:17; Acts 2:4; 18:9), and in such expressions as "He spoke saying" (cf. Mark 6:50; Heb. 2:2) sufficiently defines its force. John 8:43 brings λόγος. and λαλιά, together in a way that illustrates their respective meanings: λόγος is the matter of those discourses, the word itself; λαλιά the outward form and utterance which His word assumes. They did not understand what He said (λαλιά), because they did not take in His thought (λόγος); as it has been said, "In divine things one does not learn the definitions of words and then the things: one learns the things, and then the meaning of the words is evident." There could not be a more important principle.