1. Mutual Intelligibility: While both languages belong to the Malayo-Polynesian language family and share some vocabulary, they are not mutually intelligible. This means that speakers of one language generally cannot understand speakers of the other language without significant effort or prior exposure.
2. Phonology and Phonetics: Tagalog and Ilocano differ significantly in their sound systems (phonology) and pronunciation (phonetics). They have distinct vowel and consonant sounds, intonation patterns, and stress patterns.
3. Grammar and Syntax: While they share some grammatical features, Tagalog and Ilocano have different sentence structures, word order, and grammatical markers. For example, Tagalog utilizes a "subject-verb-object" structure, while Ilocano has a more flexible "verb-subject-object" structure.
4. Vocabulary: While there is some overlap in vocabulary, Tagalog and Ilocano have many unique words and expressions. This is due to their distinct historical development and cultural influences.
5. Historical and Cultural Context: Tagalog and Ilocano developed independently in different regions of the Philippines. They have distinct cultural histories, traditions, and influences, which are reflected in their languages.
6. Standardization and Linguistic Prestige: Tagalog has been chosen as the basis for Filipino, the national language of the Philippines. Ilocano, while spoken by a significant portion of the population, has not been given the same level of official recognition or standardization.
7. Linguistic Distance: Linguists generally classify languages based on their degree of similarity. Tagalog and Ilocano are considered to be relatively distant from each other, based on their differences in phonology, grammar, and vocabulary.
In conclusion, while both languages are part of the same language family, they have evolved into distinct entities with unique characteristics that justify their classification as separate languages.