Non-translatability (Samskrit : अननुवाद्यता) of the Samskrit words is emphasized in articles on Dharmawiki. Many translations have taken place during the colonial era which have been passed on to us, the present day generation. Many conceptual words of esoteric meaning have integrated in the daily lives of people following Sanatana Dharma and as such words do not convey the comprehensive meaning of the original samskrit word.
Shabdas (Words) are not simply sounds. They are concepts. They are visions. Unless you have an identical vision in some other language, translation becomes burden. Whitehead, eminent Harvard Mathematician and Philosopher said "All lexicographers are murderers".
So samskrit words cannot be translated. No doubt, when an Upanishadic text is taught to a student, the text itself does not mean anything. The preceptor has to drive it to the core of the disciple. He does it through Anuvada (अनुवादः), the original is a concept, not merely translated; but interpreted, annotated, and expanded with many anecdotes until the disciple "digests" the concept and the exact nuances of the word. Thus Anuvada is perpetual and eternal.
Any translation be it English or Persian (say of Dara Shikho) or the many native Bharatiya languages today tend to project a wrong orientation of the original concepts, not deliberately, but primarily because each language has its set of nuances. Although it is said that many Bharatiya languages arose from Samskrit, certain sets of words and thus concepts digressed from what was presented and intended in the mulam (primary source).
Shabda and Shabdartha
A shabda (interpreted as a word as well as sound) has a mukhya pravrutti (the main purport) according to the Vaiyyakaranas (grammarians) it is the original intended meaning. The English word 'iridescence' means a lustrous rainbowlike play of color caused by differential refraction of light waves (as from an oil slick, soap bubble, or fish scales) that tends to change as the angle of view changes. Similarly, the sun in the sky has an aura of light around him. One cannot divest him from that aura.
When a word is used, it has its own circle of meaning, light of meaning and that meaning is to be grasped especially for words like dharma and moksha. The word Moksha occurs once in the Shvetashvatara upanishad.
तं ह देवमात्मबुद्धिप्रकाशं मुमुक्षुर्वै शरणमहं प्रपद्ये ॥ १८ ॥ (Shve. Upan. 6.18) 
Mumukshuh is the desire to be liberated from miseries, liberated from bondage, liberated from poverty of thought and expression but the real greater concept into which moksha would fit is amrutattva praptih (again loosely translated as immortality).
Thus we see in one example how Moksha, cannot be translated as Liberation, Free from bondage, Emancipation, Salvation etc. None of these words can equate to or describe the concept of "Amrtattva Prapti".
Brahman is one significant concept which has been misunderstood by modern Indic interpreters who have translated IT as God. Definition of God as per English dictionary is a moral authority, a supreme being, as an image, murti or vigraha, animal or other object worshipped as divine,or symbolizing God. Conversely upanishadic definition of Brahman is a supreme existence or absolute reality. The concept of "Lord" indoctrinated into the Bharatiya system of thought processes are based on the abrahmic concept of God which is finite whereas the Brahmatattva of the deities is Infiniteness, hence God or Lord cannot be equal to Brahman.(Citation : Little Yogi in the modern city by Govinda Das)