장학금을 받는다는 것은 정말 대단한 일이에요.
[~다] in the quoting form ~다는 것 is the same as the formal, neutral-politeness sentence ending form.
It can be remembered as the "base" ending form since it's used to represent quoted phrases and formalized ideas.
This sentence ending form changes depending on whether it attaches to a verb or an adjective.
* 먹다(v) present tense sentence ending forms:
- 먹습니다 (formal, polite)
- 먹는다 (formal, plain) * base sentence ending form used for quoting.
- 먹어요 (informal, polite)
- 먹어 (informal, plain)
* 크다(adj) present tense sentence ending forms:
- 큽니다 (f, polite)
- 크다 (f, plain) * base sentence ending form - same as the adjective base form "크다" (note that no ㄴ/는 is added)
- 커요 (i, polite)
- 커 (i, plain)
* 음식을 먹는다 => 음식을 먹는다는 것은 즐거운 일이에요.
* 사는 집이 크다 => 사는 집이 크다는 것은 많은 것을 의미해요.
* 장학금을 받는다 => 장학금을 받는다는 것은 정말 대단한 일이에요.
For verbs, -ㄴ다 is attached to syllables ending in vowel or with ㄹ, in which case ㄹ is dropped and -ㄴ다 is added.
For all other syllables, -는다 attaches to the stem.
- 가다 -> 간다는 것; 하다 -> 한다는 것; 오르다 -> 오른다는 것.
- 물다 -> 문다는 것; 밀다 -> 민다는 것; 열다 -> 연다는 것.
- 먹다 -> 먹는다는 것; 읽다 -> 읽는다는 것; 죽다 -> 죽는다는 것.
For adjectives, no ㄴ/는 is added to the stem.
- 크다 -> 크다는 것; 작다 -> 작다는 것; 묽다 -> 묽다는 것; 푸르다 -> 푸르다는 것.
The ~ㄴ다 vs ~는다 variation exists to make the connected pronunciation smoother, as in many other cases with similar rules. If you study such rules noting the common principles carefully enough, you'll eventually get the hang of them, but until then you can simply memorize them.
Finally, ~은다 doesn't exist in present tense sentence endings as described above.
~은 however appears when verbs and adjectives are turned to noun-modifying adjectival forms.
- 먹다 -> 먹은 => past tense or resultant state(present perfect) adjectival form of verbs (compare with 하다 -> 한).
- 크다 -> 큰 => present tense noun-modifying forms of adjectives.
Check grammar books and sites to fully understand this rather involved subject.