The current study investigates the expression of progressive and habitual aspect in second language Spanish, integrating theoretical insights from usage-based and concept-oriented approaches to second language acquisition, along with quantitative sociolinguistic methods. To address the full breadth of forms involved, the study examines variation between synthetic (e.g., "como" "I eat") and analytic forms (e.g., "estoy comiendo" "I am eating") when fulfilling the same communicative function. The study used an experimental, cross-sectional design by testing college-level learners enrolled in four different levels in a Spanish-language sequence to uncover developmental patterns (N = 80), along with a group of L1 Spanish speakers who served as a baseline (N = 20). To assess both receptive and productive language skills and ensure that attested effects were not solely due to the task employed, the study triangulated an oral picture narration task, a written contextualized preference task, and a written interpretation task. Likewise, to contribute novel insight on tense-aspect acquisition, the study incorporated past, present, and future temporalities into all elicitation tasks. The results showed that all participant groups used synthetic forms more frequently than analytic forms, particularly in oral production. Generalized linear mixed-effects modeling revealed that learners adopted increasingly systematic patterns of use or preference with increases in course level, with analytic forms generally favored with dynamic predicates and low-frequency verbs, and generally disfavored in future-time contexts. However, target-like interpretation of the forms lagged behind preference or production, as learners did not make a significant association between forms and prototypical interpretations until an advanced stage in the learning sequence. Proposed developmental stages and pedagogical implications for instruction on the synthetic and analytic contrast are also discussed. Altogether, the dissertation demonstrated the benefits of expanding tense-mood-aspect acquisition research from one-to-one to multifunctional form-meaning connections using analyticity as a gauge for synchronic morphosyntactic variation patterns. This approach made it possible to observe interlanguage restructuring associated with increases in proficiency, frequency effects that were affected by variable operationalization, and that the deployment of synthetic and analytic forms varied by temporality, complementing prior work focused primarily on the present tense. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]