What is the difference between nama-rupa and the five skandhas? As I understood it from the abhidharma, nama-rupa is just another way of looking at the five skandhas, a different scheme for the same thing, along with others (e.g. the dhatus).

But, as far as I can tell, this is never quite explicitly stated.

Why?

And are they identical ways of saying the same thing?
Nama-rupa &amp; the five aggregates are taught for different purposes. 

The five aggregates are objects of insight. 


  'Such is form, such its origination, such its passing away. Such is feeling, such its origination, such its passing away. Such is
  perception, such its origination, such its passing away. Such are
  fabrications, such their origination, such their passing away. Such is
  consciousness, such its origination, such its disappearance.' ...AN 4.41


Nama-rupa is a condition in Dependent Origination, where it serves as the 'control centre' for meditation. Either nama-rupa is overcome by ignorance or nama-rupa is controlled to end ignorance.


  He sits down folding his legs crosswise, holding his body [rupa] erect and setting mindfulness [nama] to the fore....MN 118
  
  He lives with attention to body [rupa] established, with an immeasurable mind [nama]...MN 38


Nama-rupa is 'mentality-materiality' &amp; excludes consciousness (although includes internal contact, which includes consciousness one of three constituents but predominantly the mind/mano as a sense organ).


  What is mentality-materiality (nama-rupa)? Feeling, perception, volition, contact and attention — these are called mentality. The four great elements
  and the material form derived from the four great elements — these are
  called materiality.
  
  What is consciousness? There are these six classes of consciousness: eye-consciousness, ear-consciousness, nose-consciousness,
  tongue-consciousness, body-consciousness, mind-consciousness. 
  
  SN 12.2 &amp; MN 9


Nama = mentality. It also includes another mental functions, such as mindfulness, zeal, energy, persistence, decision, etc (as listed in MN 111). 

Why consciousness is kept separate is because consciousness is mere sense awareness, like a mirror. It is essentially 'passive' in nature. 

Where as 'nama' is like 'intelligence'. It is a grouping of those functions of mind that discern, develop wisdom &amp; makes decisions. Otherwise, if nama does not develop wisdom, it is controlled by ignorance (avicca paccaya...nama-rupa).

'Nama-rupa' is used as a word-compound to show nama &amp; rupa are inseparably interrelated. For example, when nama becomes agitated, rupa simultaneously becomes agitated. 


  His bodily disturbances &amp; mental disturbances grow. His bodily torments &amp; mental torments grow. His bodily distresses &amp; mental
  distresses grow. He is sensitive both to bodily stress &amp; mental
  stress.
  MN 149


Where as consciousness is just awareness or objectivity. Consciousness does not produce suffering where as an ignorant 'nama' produces &amp; is afflicted by suffering; which also afflicts the physical body. 

~~~

'Nama-rupa' is also a pre-Buddhist-Brahmanistic term that the Buddha adopted, redefined &amp; thus debunked. 

Brahmanism was concerned with 'creationism', of how the mind names forms. In Brahmanism, nama-rupa is 'name-form'. Where as the Buddha said 'nama-rupa' is 'mind-body' (mentality-materiality), which should be observed in meditation so to understand how suffering afflicts the mind-body &amp; also can cease in the mind-body. 


  Yet it is just within this fathom-long body, with its perception &amp; intellect, that I declare that there is the world/suffering, the
  origination of the world/suffering, the cessation of the
  world/suffering and the path of practice leading to the cessation of
  the world/suffering... AN 4.45


There are many scriptures where the Buddha talks to Brahmans and the word 'nama-rupa' retains its Brahmanistic meaning as 'name-form'. This causes confusion to most Buddhists &amp; scholars, who incorrectly translate nama-rupa as 'name-form' in all contexts. 

When the Buddha teaches Buddhists, the translation is 'mentality-materiality'. When the Buddha teaches Brahmans, the translation is 'name-form'. 


  The brahman Jata Bharadvaja went to the Blessed One and said: Gotama, I ask you this: who can untangle this tangle?
  
  Where name-&amp;-form,   along with perception   of impingement &amp; form, totally stop without trace:  that's where the tangle         is cut.
  
  When this was said, the brahman Jata Bharadvaja said to the Blessed One, "Magnificent, Master Gotama! Magnificent!
  
  SN 7.6