SN 5.56.19
The Buddha tells the bhikkhus that each of the four truths is capable of unlimited ways of being expressed.
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Index of Available translations: SN 5.56.19
The key term here is: sankāsanā. Also spelled: saṅkāsanā and sañkāsanā. I have spelled it as it is found in PED which defines it: "explanation, illustration."
Both Woodward and Bhk. Bodhi note commentary as stating that synonyms are (PED definitions in ()):
pakāsanā = (explaining, making known; information, evidence, explanation, publicity),
vivaraṇā = (uncovering, unveiling, making open, revelation),
vibhājan'uttānī-karaṇa = (division; detailing, classification 'stretch out, flat-make (to make plain)),
paññatti = (making known, manifestation, description, designation, name, idea, notion, concept).
In Childers', 'saṅkāso' = resembling.
For each, Gotama states that:
Tattha aparimāṇā vaṇṇā,||
aparimāṇā vyañjanā,||
aparimāṇā sankāsanā,||
Such is immeasurably colored or shaded (Woodward: 'shades'; Bhk. Bodhi: 'nuances')
immeasurably characterized (Woodward: variations of meaning; Bhk. Bodhi: details),
immeasurably sankāsanā-ed (Woodward: 'ways of illustrating'; Bhk. Bodhi: 'implications'.)
I suggest the meaning is to be inferred from the previous suttas where, for example, 'dukkha' is defined in one sutta as the 'khandhas' and another as the 'internal six realms'. In other words he is explaining this business of the interchangeability of various aspects of Dhamma.
I further suggest that this is not to say that 'dukkha' or any other important term may be translated any which way or any way other than that which is most precisely aligned with its literal meaning (I believe that is being warned against in SN 5.56.16), but that when that term is found, the concept expressed by it may be explained by other terms or other ideas equated to it without altering its meaning. There is a fine line there which must be respected between defining a term as such and such and equating such and such to that term.
'Dukkha' means 'dukkha' not 'vihesā'.
'Dukkha' encompasses 'vihesā',
'vihesā' does not encompass 'Dukkha'.
'Pain' means 'pain', not 'worry'.
'Pain' encompasses 'worry'.
'Worry (or stress or anguish) does not encompass 'pain.'
One way of understanding 'Dukkha' is to know that 'idaṅ' or the 'saḷ-āyatanāna' or 'khandha' is Dukkha;.
One way of understanding 'pain' is to know that 'This' (whatever) or 'the realm of the senses' or 'the components of existence' are 'pain'.
What makes these equivalents 'legal,' and not narrow, non-literal, abstract translations is that what the Buddha is saying in these cases is that every term that is equivalent to 'every existing thing' is capable of being understood as 'pain' whereas not every thing that is painful is capable of being understood to encompass all understandings of the term pain.
Why is this important for the practitioner?
Because when you are told 'thou shalt not kill' and you follow the commandment to avoid the wrath of God, you will behave differently than when you are told 'train yourself to abstain from harm to living beings' and you follow that advice pointing to your own best self-interest.
For more on this see the introduction to my translation of the next sutta, SN 5.56.20.
