Ancient Hebrew's closest relations are other Canaanite languages such as Phoenecian, Moabite, Ammonite, Edomite and the likes. Modern Hebrew has also had a lot of influence in pronunciation, vocabulary and grammar from various European languages and is a very different animal from Classical Hebrew as in many ways it had to be reconstructed.
Aramaic is also not one monolithic language either, but rather a language family with hundreds of members (traditionally called "dialects"),
many of which are not mutually intelligible or even written using the same alphabet.
In a nutshell: Jewish Aramaic dialects, of course, are more intelligible to Hebrew speakers as vocabulary has been borrowed back and forth (for a quick example, "Bar Mitzvah" isn't Hebrew, it's Aramaic; if it were "100% Hebrew" it would have been "Ben Mitzvah") and this borrowing started back during the Exile to Babylon where the Jews were forced (as a matter of survival) to adopt Late Imperial Aramaic as their lingua franca.
In later years, starting with the decline of the Persian Empire, Aramaic underwent a fracturing (much like Latin after the fall of Rome into romance languages) and each small pocket of dialects evolved separately from one-another. The split was even down religious lines as Jewish and Christian Aramaic dialects that grew up side-by-side in the same village became completely incomprehensible due to vocabulary and phonemic shifts in small increments over thousands of years.
However, between Aramaic and Hebrew (despite seeing whether the text is written in Syriac, Mandaic, or Nabatean Aramaic scripts, for example) there are generally the following 'readily spotted' differences:
-
Use of the Particle די (di) "Of" - In Hebrew you'd find של (shel) or the Construct state employed to denote genitive relationships. In Aramaic די (
di) (more often as a prefix ד (di-,de-,da-) or in older dialects spelled זי (
di)) is used for a variety of things from denoting genitive relationships to possession to introducing direct speech.
-
The Emphatic form - How definite nouns are constructed. In Hebrew it's the prefix ה (
ha-) where in Aramaic it's the suffix א (
-a). In later Eastern dialects, the Emphatic form lost its definiteness and became the base form for words, definiteness usually denoted by a proleptic suffix plus די (di) (for example, טורה דמלכתא (
turah d'malktha) "the queen's mountain" literally "her mountain, that of the queen"). In some modern dialects, such as Turoyo, they have re-invented a separate definite article and place it upon the Emphatic.
-
Plural Nouns - In Hebrew you generally get ים (
-im) for the masculine and ות (
-ot,-oth,-os) for the feminine endings. In Aramaic they are (depending on dialect) ין (
-in) in the Absolute or יא (
-aya) or א (
-e) in the Emphatic for the masculine and ת (
-ath) in the Absolute or תא (
-ata,
-atha) in the Emphatic for the Feminine.
-
Pronouns - In Hebrew we find אני (
ani) "I", אנחנו/אנו (
anahnu/anu) "we", אתם (
atem) "you" [masc.], הם/הן (
hem [masc.],hen [fem.]) "they." Where in Aramaic we see אנא/אנה (
ana,ena,anah) "I", אנחנה/אנחנא/אנחנן/חנן/אנן (
enahnah,enahna,enahnan,hnan,enan) "we", אתון (
atun) "you" [masc.], הנון/הנין (
henun [masc.],
henen [fem.]). Posessive and demonstrative pronouns are also different.
And where there are a heck of a lot more (like I said, these are the quickest to spot).
