1]There are eleven vowels and thirty three consonants in Hindi, whereas there are thirteen vowels and thirty three consonants in Sanskrit.
2]There are three Numbers in Sanskrit. They are Singular, Dual and Plural. Only more than two are considered Plural. In Hindi, there are only two numbers. They are Singular and Plural.
3]There are three genders in Sanskrit. They are Masculine, Feminine and Neutral. In Hindi there are just Masculine and Feminine genders.
4] In Hindi, the verb changes according to person, number and gender. In Sanskrit, the verb changes according to person and number only. It does not change according to gender.
5] In Hindi the last syllable of the word is pronounced half, whereas in Sanskrit, it is pronounced completely unless marked by ‘Halant’ . Halant is a symbol to pronounce the syllable half.
6]There are only two types of vowels in Hindi. They are Short and long vowels [Hrasva and Deergha svaras]. In Sanskrit, there are three types of vowels; Hrasva, Deergha and Pluta. Pluta is an elongated vowel. Eg: Raaaamaaa, Krishnaaaa, Aagachchaaaa, etc
7]One remarkable difference between the two is with regard to case endings. Unlike Hindi, Sanskrit is an inflecting language.
8]Because Sanskrit is an inflecting language, word order does not matter at all. In Hindi, word order matters.

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Similarities & differences in Hindi and Sanskrit

Sanskrit Sentences with meaning in Hindi and English
I am a student.
मैं एक छात्र हूँ।
अहम् एकः छात्रः अस्मि।

You are a student(female).
तुम एक छात्रा हो।
त्वम् एका छात्रा असि।

Ram is a student.
राम एक छात्र है।
रामः एकः छात्रः अस्ति।

I go to school.
मै स्कूल जाता हूँ।
अहम् विद्यालयम् गच्छामि।

You go to school.
तुम स्कूल जाती हो।
त्वम् विद्यालयम् गच्छसि।

He goes to school.
वह स्कूल जाता है।
सः विद्यालयम् गच्छाति।

I read in class 10.
मैं दसवी कक्षा में पढ़ता हूँ।
अहम् दशमी – कक्षायाम् पठामि।

You read in class 10th.
तुम दसवी कक्षा में पढ़ती हो।
त्वम् दशमी कक्षायाम् पठसि। 

He reads in class 10.
वह दसवी कक्षा में पढ़ता है।
सः दशमी  – कक्षायाम् पठति।

He eats fruit.
वह फल खाता है।
सः फलमः खादति।

Student writes with a pen.
छात्र कलम से लिखता है।
छात्रः कलमेन लिखति।

I give money to the poor.
मैं गरीब को धन देता हूँ।
अहम् निधानाय धनम् यच्छामि।

चिड़िया पेड़ पर बैठी है।
The bird is sitting on the tree.
चटका वृक्षम् तिष्ठति ।

He plays in the playground.
वह खेल के मैदान में खेलता है।
सः क्रीडाङ्गणे खेलति।

Simple Sentences in Hindi(Sanskrit and English)

Hindi Consonants

क	ka
ख	Kha
ग	Ga
घ	Gha
ङ	nga
च	cha
छ	chha
ज	ja
झ	jha
ञ	nja
ट	Ta
ठ	Tha
ड	Da
ढ	Dha
ण	Na
ड़	ugDha
ढ़	ugDhha
त	ta
थ	tha
द	da
ध	dha
न	na
प	pa
फ	pha
ब	ba
भ	bha
म	ma
य	ya
र	ra
ल	la
व	wa
श	sha
ष	shha
स	sa
ह	ha
क्ष	ksh
त्र	tra
ज्ञ	gya

Hindi Consonants...

Hindi Vowels	
अ	                                      a
आ	                                      aa
इ	                                      i
ई	                                      ii
उ	                                      u
ऊ	                                      oo
ए	                                      e
ऐ	                                      ai
ओ	                                      o
औ	                                      au
अं	                                      am
अ:	                                      aha
ऋ	                                      ri

Hindi Vowels...

Hello friends! Greetings of the day! In Hindi, instead of using मैं - मेरा, तू - तेरा, हम - हमारा, we use मैं अपना, तू अपना, हम अपना while using reflexive pronoun to avoid confusion. 